Conglomerate with 9 companies is so great. I under

Conglomerate with 9 companies is so great. I understand a lot and can see that we have a really strong buy I just want to learn more about level2 I have watched videos and understand alot about trading and the concept of level2 it just seems really odd to me that someone would sell any shares at all unvc first of all especially if is for less than the bid or than they could make it actually seems stupid.