P(x) is a mathematical notation used to represent a polynomial function, where "P" stands for the polynomial and "x" is the variable. A polynomial is an expression made up of variables raised to whole number powers, along with coefficients. For example, P(x) could be expressed as P(x) = 2x² + 3x + 5, where the coefficients are 2, 3, and 5. Polynomials can be classified by their degree, which is the highest power of the variable. For instance, the degree of P(x) = 2x² + 3x + 5 is 2. Polynomials are fundamental in algebra and are used in various fields, including physics, engineering, and economics.