In config files (an addon's config.cpp or a mission's Description.ext), a Boolean value is expressed as a number, which is either 0 (false) or 1 (true).
In scripts, a Boolean is a unique type, and contains either false or true.
It is returned by some commands (e.g. alive) or Boolean operation (e.g. if (3>2) then), and can be assigned to variables (e.g. _isAlive = alive tank1).