Maxima is a command-line system. You enter a command, obtain an answer and can enter the next command.
A command is an expression that can be spread over many lines and is closed with a semicolon. e.g.
(%i1) 14*(7 + 3);
You obtain this answer:
Note that nothing will happen when you forget to enter the semicolon. Maxiama will simply wait for further input
You can enter an expression that contains variables:
(%i2) (x + 2)*(x - 3);
Maxima answers this expression in unsimplified form:
(%o2) (x - 3) (x + 2)
Note that you have to type an asterix to denote multiplication. Maxima prefers a writing form that does not use a multiplication operator: Like in traditional mathematical notation, multiplication is implicit.
Perhaps you would prefer to see the product expanded. This is something that you have to ask for.
2 (%o5) x - x - 6
Note the interpretation of powers:
81 (%o2) x
12 (%o4) x
We see that x^3^4 is evaluated as x^(3^4), not as (x^3)^4.