Operands and Expressions
An "operand" is an entity on which an operator acts. An "expression" is a sequence of operators and operands that performs any combination of these actions:
Computes a value
Designates an object or function
Generates side effects
Operands in C include constants, identifiers, strings, function calls, subscript expressions, member-selection expressions, and complex expressions formed by combining operands with operators or by enclosing operands in parentheses. The syntax for these operands is given in Primary Expressions.