Question

what are polynomials

Answer 1

Polynomials are sums of these "variables and exponents" expressions. Each piece of the polynomial, each part that is being added, is called a "term". Polynomial terms have variables which are raised to whole-number exponents (or else the terms are just plain numbers); there are no square roots of variables, no fractional powers, and no variables in the denominator of any fractions

Answer 2

A polynomial is a mathematical expression consisting of a sum of terms, each term including a variable or variables raised to a power and multiplied by a coefficient.
Some polynomials have two, three, or more variables.  A two-variable polynomial is called bivariate; a three-variable polynomial is called trivariate..