Can someone explain what a highest common factor in Algebra is?

See below.

Step-by-step explanation:

Yes it is the highest value factor that will divide into 2 or more algebraic expressions.

For example

x^2 and x^3 have HCF = x^2.

3y^2 and 6y have HCF = 3y.

4xy^2 and 6 x^2y^2 have an HCF = 2xy^2.