To start editing a cell you can select Edit link in context menu on view table page or initiate editting from edit view by
When editor is active you can save new value and close editor by pressing Enter or clicking a mouse at any place
of the page outside the editor (the only exception to this is Multiline editor - to close it with saving entered value you
need to press Ctrl+Enter)
To close editor without saving press Esc.
One of the editors is text editor. It understands Alt+Enter (Ctrl+Enter for Opera) key combination to switch to multiline editor.