Like terms are any terms that have the same variable value.
In the sequence 8a, b^2, b^3, 4b^2, 4, and 5a, the like terms are the ones that have the same variable to the same power.
8a and 5a are like terms, as well as b^2 and 4b^2, because both sets of terms have the same variable.
Hope that helped =)
