A QuickBook document is composed of one or more blocks. An example of a block is the paragraph or a C++ code snippet. Some blocks have special mark-ups. Blocks, except code snippets which have their own grammar (C++ or Python), are composed of one or more phrases. A phrase can be a simple contiguous run of characters. Phrases can have special mark-ups. Marked up phrases can recursively contain other phrases, but cannot contain blocks. A terminal is a self contained block-level or phrase-level element that does not nest anything.

Blocks, in general, are delimited by two end-of-lines (the block terminator). Phrases in each block cannot contain a block terminator. This way, syntax errors such as un-matched closing brackets do not go haywire and corrupt anything past a single block.