Boolexpr vs. boolean?

Does anyone know what the difference between boolean and boolexpr is?

boolexpr can also be a condition function
for example Condition(function Whatever)

or a filterfunc
Filter(function Whatever)

where whatever would be a function taking nothing and returning a boolean

I believe that boolexprs can also be used in conjunction to create
new boolexprs. I haven't tested this, but I'm quite sure it works.

bxp = And(bxp1, bxp2)

bxp = Not(bxp1)

bxp = Or(bxp1, bxp2)

The function(s) in a boolexpression are run every time it is
evaluated.

Boolean is 1 byte variable, but boolexpr is a pointer (reference) to function, which returns boolean.