They are excellent teachers because learning a word and remembering a word are two different things. You can remember what a word means but not how to say it. You do this in your own language with words that are not repeated enough for you to use them. Repetition is what sparks remembering.
Word games that teach through multiple-choice are a great learning tool. You eliminate from what you know which is reinforcing what you know, and you guess from what you don’t know at all times reinforcing and pushing your memory.
Learning to spell foreign words in phonetic or native spelling is also a great way to help remember words.
After words are learned word games are a vital way to review what you learned because like the words in your own language if you don’t use them you lose them.
Try the word game at World Word Exchange. It’s designed to make learning and remembering a new language as easy as possible.