Undo

This will undo the last editing operation you performed to your project. Audacity currently supports full unlimited undo - meaning you can undo every editing operation back to when you opened the window.

Redo

This will redo any editing operations that were just undone. After you perform a new editing operation, you can no longer redo the operations that were undone.

Cut

Removes the selected audio data and places it on the clipboard. Only one "thing" can be on the clipboard at a time, but it may contain multiple tracks.

Copy

Copies the selected audio data to the clipboard without removing it from the project.

Paste

Inserts whatever is on the clipboard at the position of the selection cursor in the project, replacing whatever audio data is currently selected, if any.

Trim

Deletes everything but the selection.

Delete

Removes the audio data that is currently selected without copying it to the clipboard.

Silence

Erases the audio data currently selected, replacing it with silence instead of removing it completely.

Split

Moves the selected region into its own track or tracks, replacing the affected portion of the original track with silence. See the figure below:

Duplicate

Makes a copy of all or part of a track or set of tracks into new tracks. See the figure below:

Select... > All

Selects all of the audio in all of the tracks.

Select... > Start to Cursor

Selects all the audio from the start of the timeline to the current cursor.

Select... > Cursor to End

Selects all the audio from the cursor to the end of project, which is as far as audio exists in the project.

Find Zero Crossings

Moves the cursor or the edges of the selection to the nearest point where the audio waveform passes though zero. Use this to help achieve click-free cuts in audio, as the two ends of the cut will exactly line up.

Selection Save

Saves the current selection and position. This function only saves the selection boundaries, but not the actual audio data.

Selection Restore

Restores the selection to the project. You need to have an existing selection for this to work.

Move Cursor...

These commands provide quick and accurate ways to manoeuvre the cursor around the project to the start and end of tracks and selections.

Snap-To...

Turns snapping of the cursor to a grid of time values on or off. When off, your cursor can be positioned on any sample in the audio file. When on, it is restricted to certain points in time, determined by the time format in use. This is useful if your project must follow an external timecode exactly.