Question 150996
"Like terms" are terms that contains the same variable or variables raised to the same powers.

For instance, if you have a variable x raised to several different powers (x , x^2, x^3), then like terms are those with the same exponent. Think of it this way, if you have boards, sheets of plywood and boxes (x, x^2, x^3), you can group the boards with other boards, the plywood with other plywood and the boxes with other boxes. But it makes no sense to collect boards (lines), plywood (area) and boxes (volume) together. Their dimensions are different, they are not 'like terms'.

Similarly, if you have an expression like x^2 + xy + y^2, all the terms are different. There are no like terms there. However, if you had x^2 + xy + y^2 + 6x^2, the x^2 terms are like terms and can be added directly to get 7x^2