I hear the terms high and low floors as well as high and low ceilings associated with draft picks bandied about quite a bit lately on CB. Not sure what they meant. Did a Google search and this is what I believe they mean. Feel free to correct, add, or delete info if I am off a bit.
A player with a low floor is one with little success at the pre-NBA level. For example, Dragan Bender, Thon Maker, Zhou Qi.
A player with high ceilings are those who could potentially turn into stars or get significantly better in the future. Again, Bender, Maker and Qi make the list.
Thus, these players are generally considered low floor-high ceiling players.
Someone with significant success at the college level would be considered having a high floor, e.g., Buddy Hield, Jamal Murray, Kris Dunn.
Of these Kris Dunn might be considered to have the highest overall ceiling because of his more elite athleticism and better skill set. Hield and Murray would have a higher ceiling offensively because of their better shooting skills.
A player with a low ceiling is one who most feel will not get much better at the NBA level and has reached his growth potential. Jaylen Brown might fit this description because many think he lacks true basketball talent even though he's a gifted athlete.
Jaylen was successful in college. Thus, he is considered to be a high floor-low ceiling player.
I think I better understand what these terms now mean. But, feel free to correct or clarify them better if you wish.