An assignment is an expression that stores a new value into a variable. After this expression is executed, the variable z has the value 1. Whatever old value z had before the assignment is forgotten.
Assignments can store string values also.
It is the simplest assignment operator because the value of the right-hand operand is stored unchanged. If you ignore the value, you might as well not use the operator. An assignment operator is different. It does produce a value, but even if you ignore the value, the assignment still makes itself felt through the alteration of the variable. We call this a side effect .