Expression combines both operators and operands.
An expression is the combination of operators, constants and variables that is evaluated to get a result. The result pf expression is either string data, numeric data or logical value that can be stored in a variable.
There are 3 types of expressions:
Arithmetic expressions
LET A=B+C
LET AVG = SUM/3
Rational expressions
IF A>B THEN G=A
Logical expressions
IF A>B AND A>C THEN G=A