Command syntax is laid out with a combination of <> , [] , ... and |.
Angle brackets (<>) indicate a required argument.
For example, in /kit delete <name>, The second argument is required.
Square brackets ([]) indicate an optional argument.
For example, in /kit bind [add | remove][key], the second argument is optional, and, if provided, can be either add or remove.
An ellipsis (...) indicates a remainder argument, meaning that any arguments past that one are included in the argument.
For example, in /warn <player><reason...> , reason is a remainder, so /warn 76561198267927009 Too good, probably cheating. would be valid.
Bars (|) indicate a choice between two arguments.
For exmaple, in /load <build | ammo>[amount | half], the first argument can either be build or ammo. The second argument is optional and could be an amount, or half.