Mostly intended for creative or development. This is similar in spirit to using a chain of command blocks, but more portable and with easier setup.
Write commands into a book-and-quill, one command per lines. To execute the commands, hold the book in your off-hand, and use a stick in your main hand. All commands are run in succession, even if one fails along the way.
The book's user is considered the source of the commands. Usage of books can be locked behind a specific permission level; by default 2 (Game Master).