The main difference between the Nasdaq 100 and the Nasdaq composite index is that the latter tracks all the companies listed on the Nasdaq stock exchange, whereas, the Nasdaq 100 tracks only the top 107 companies listed on the stock exchange on the basis of market capitalization.
This rally started off Dec 2018 low is wave (A) of ( 5 ) targeting the previous top reached in August 2018. It shall be subdivided into five waves. It seems that it has not completed the strongest part of the rally in wave ( iii ) up. The next cluster of fins that could stop it is at 7,850. But wave ( iii ) up may easily overshoot that channel only to come back down in wave ( iv ) up.