Nearly all things one deals with in GAP are objects. For example, an integer is an object, as is a list of integers, a matrix, a permutation, a function, a list of functions, a record, a group, a coset or a conjugacy class in a group.
Examples of things that are not objects are
comments which are only lexical constructs,
while loops which are only syntactical constructs,
and expressions, such as 1 + 1;
but note that the value of an expression, in this case the integer 2,
is an object.
Objects can be assigned to variables, and everything that can be assigned to a variable is an object. Analogously, objects can be used as arguments of functions, and can be returned by functions.
IsObject( obj ) C
IsObject returns true if the object obj is an object. Obviously it
can never return false.
It can be used as a filter in InstallMethod
(see Method Installation in ``Programming in GAP'')
when one of the arguments can be anything.
GAP 4 manual