***** NOT A TEACHER *****
As you know, the word "complement" comes from "to complete."
"Tom painted the house" is a good sentence.
"Tom painted the house red" is also a good sentence. The speaker wants to tell you the color that was used. As you can easily guess, "red" must be complementing "house."
Maybe you can post two or three sentences that confuse you. (I remember your excellent post regarding what an infinitive modifies. I am VERY eager to see your questions about objective complements.)