I would reckon they mean something like the Legendre Polynomials.

Say we have some vector space we can call and its

inner product is

If we use the Gram-Schmidt process to to transform the standard basis,

, into an orthonormal basis.

The polynomials in the resulting basis are called theNormalized

Legendre Polynomials.

Go ahead and google Legendre Polynomials and you will find plenty.

There is an easy way to find them called Rodrigues's Formula.

Like a unit vector, a normalized function has length 1.