There are items to cancel the operation or select range.
Undo
It cancels the previous operation.
Redo
It cancels [Undo].
Select All
It selects all vertices, lines, and faces.
Invert all the selection of vertices
It inverts the selected condition of all vertices.
Invert al the selection of faces
It inverts the selected condition of all faces.
Unselect all
It unselects all vertices, lines, and faces.
Select all in a current object
It selects all vertices, lines, and faces of a current object.
Before
After
Invert all the selection of vertices in a current object
It inverts all the selection of vertices in a current object.
Invert all the selection of faces in a current object
It inverts all the selection of faces in a current object.
Unselect All in a current object
It unselects all vertices, lines, and faces of a current object.
Select all the faces in a current Material
It selects all the faces that the current material is assigned to.
Unselect all the faces in a current material
It unselects all the faces that the current material is assigned to.
Lock selection
When you check this, you cannot select or unselect while using [Select], [Move] command and so on. But it can be used for a part of commands and not for all commands. And it does not affect the operation on Menu.