Hi @damasop2021 and welcome to Steem! A whale is a huge account, and his or her full vote is generally worth significantly more than most other accounts. It is also very influential in other ways, like having an almost decisive weight on who the top witnesses are, or which Steem Proposals get funded, if they choose to exert their power. At the same time, as taskmaster explained in his post, one can be a "small fish" in Steem Power, but a whale in a specific tribe (like steemleo or palnet etc).