What are the differences between precedence and associativity?

Precedence rules specify priority of operators (which operators will be evaluated first, e.g. multiplication has higher precedence than addition, PEMDAS).

The associativity rules tell how the operators of same precedence are grouped. Arithmetic operators are left-associative, but the assignment is right associative (e.g. a = b = c will be evaluated as b = c, a = b).