Emacs is a programmable environment built around buffers and commands. A file is displayed through a buffer, a buffer is displayed in one or more windows, and windows belong to graphical or terminal frames.

The cursor position is called point. The mark stores another position. When point and mark delimit active text, that text is the region. Most editing commands operate at point, on the region, or on a syntactic unit determined by the active mode.

Emacs documentation uses C- for Control, M- for Meta, S- for Shift, RET for Return, SPC for Space, TAB for Tab, and DEL for Backspace. Meta is normally Alt or Option; pressing Escape before a key can also enter a Meta key.

A key sequence invokes a named command. Prefix keys such as C-x, C-c, and C-h begin larger keymaps rather than immediately performing an operation. M-x invokes a command by its name, which makes every interactive command accessible even when it has no key binding.

Every buffer has one major mode that defines its primary editing behavior. A buffer can also have any number of minor modes that add focused features such as automatic filling, syntax checking, or visual line wrapping.

Modes contribute key bindings, menus, syntax rules, indentation, font locking, and hooks. The mode line shows the active major mode and usually abbreviates active minor modes.

Emacs is designed to explain its current state. Help commands inspect the exact running command, variable, keymap, and mode rather than requiring you to memorize a static configuration.

When a key behaves unexpectedly, describe the key and inspect the active modes. When you know the desired action but not its name, use apropos or search the Info manual.

Visiting a file creates or reuses a buffer whose contents correspond to that file. Editing changes the buffer; saving writes those changes to storage. Non-file buffers hold help, process output, messages, directories, or temporary text.

Buffer names and file names are related but distinct. Two files with the same base name receive distinct buffer names, and a buffer can be renamed without renaming its file.

An Emacs window is a pane inside a frame, not an operating-system window. Multiple windows can show the same buffer at different positions, and display commands choose where buffers appear without changing the buffer itself.

Frames are top-level displays. Tab bars store reusable window configurations within a frame; they do not replace buffers.

Deletion removes text without normally saving it. Killing removes text and records it in the kill ring. Consecutive kill commands can append to one kill-ring entry, allowing larger units to be assembled and yanked later.

Yanking inserts a kill-ring entry. Immediately following a yank with M-y rotates through older entries. Emacs undo records buffer changes as a sequence and can itself be interrupted and traversed.

C-SPC records the current point as the mark. Moving point then creates a region. Transient Mark mode visually highlights active regions and lets region-aware commands distinguish active selections from inactive marks.

Emacs keeps a mark ring, so previous marks can be revisited. Narrowing temporarily restricts editing and display to part of a buffer; widening restores the accessible portion.

Incremental search updates the match as the search string is typed. Repeating the search key moves to another match, RET accepts the location, and C-g backs out or cancels.

Query replace asks before each replacement. Regular-expression variants use Emacs regular-expression syntax, whose escaping can differ from PCRE, JavaScript, and shell tools.

The minibuffer reads command arguments such as file names, buffers, commands, variables, and search patterns. Its completion category determines which candidates and matching rules apply.

Minibuffer histories are usually separate by argument type. Reusing history is often faster and safer than retyping a path or command.

Registers are named single-character slots that can store text, positions, numbers, rectangles, window configurations, and other values. They are useful for deliberate temporary storage outside the kill ring.

Rectangle commands treat a region as columns spanning multiple lines. Rectangle Mark mode provides interactive rectangular selection and editing.

Dired is Emacs’s directory editor. A Dired buffer lists files and lets commands operate on the file at point, marked files, or files selected by a prefix argument.

Marking and flagging are different: marks select files for general commands, while deletion flags queue files for removal by x.

Emacs programming modes provide syntax-aware movement, indentation, comments, and commands. Xref supplies a common interface for definitions and references, project.el identifies projects, Compilation mode navigates diagnostics, and Eglot integrates language servers.

The available backend depends on the active major mode, project files, tags, language server, and installed external tools.

Emacs can invoke one-off commands, filter regions, and host interactive process buffers. shell-mode sends input through a shell process using comint, while term and ansi-term provide terminal-style character handling.

Process buffers are normal Emacs buffers with mode-specific bindings. Their working directory, environment, coding system, and process state affect command behavior.

Emacs behavior is controlled by variables, faces, hooks, and keymaps. The Customize interface discovers options and records selected values, while an init file can express configuration directly in Emacs Lisp.

Prefer documented customization variables and public functions over changing internal implementation details. Apply mode-specific behavior through hooks and mode keymaps rather than globally when possible.

Emacs reads a user init file during normal startup. Common locations include ~/.emacs, ~/.emacs.d/init.el, and ~/.config/emacs/init.el; the exact selected file is available in the user-init-file variable.

Configuration is Emacs Lisp. Forms can be evaluated interactively while developing, then placed in the init file after their behavior is understood.

package.el installs and manages Emacs Lisp packages from configured archives. Emacs also ships many built-in libraries that can be loaded without installing an external package.

Archive contents are code executed with the user’s permissions. Review archive trust, package provenance, signatures, and update changes as part of normal dependency management.

An Emacs server lets external emacsclient processes ask an existing Emacs instance to visit files or evaluate expressions. This avoids starting and initializing a new instance for each editor request.

A daemon starts without an initial graphical frame. Clients can create frames as needed. Server authentication data identifies the server and must remain protected.

Start by separating configuration problems from Emacs itself. A quick startup without the user init file and site file provides a clean comparison. Messages, command descriptions, active modes, and recent input usually reveal which component changed behavior.

Autosave data can recover edits after a crash. Backup files preserve earlier saved contents. Their names and locations depend on the active autosave and backup configuration.