☞It is any valid combination of operators and operands that represents a value.
☞It is composed of one or more operations.
☞Examples : 15, 2.4, a+12, x>y, 3+4>4-6, x = 8 etc.
☞lvalues are the objects to which you can assign a value or expression. They come on the LHS ( Left Hand Side ) of an assignment statement.
☞rvalues are the literals and expressions that are assigned to Lvalues. They come on the RHS ( Right Hand Side ) of an assignment statement.
☞Example : x = 8 ( x is Lvalue whereas 8 is Rvalue )
☞Some invalid expressions : 20 = a; 10 * 5 = c, etc