It's confusing because the name doesn't really align with how it's typically rewarded. I agree with
FredMertz that it's most often best player but with some situation specific caveats. The most common caveat is around team performance, It's typically the best player on a good team. I have rarely seem an MVP given to the best player that happened to be on a terrible team that missed the playoffs for example. I also think in most major American sports it tends to be best offensive player more often that not. Winning the award for a position like Goalie would typically take some kind of statistically historic performance like most shut outs ever.
It gets even messier when you get into some of the "its this guy's turn" habits of voters which happens a lot in the NBA. Karl Malone won MVP over Jordan one year just because the voters got tired of voting for Jordan. This year when James Harden and Giannas both had amazing seasons a lot of people said they'd vote for Giannas because Harden got his MVP last year and they voted for Harden the year before because he should have won the year before that.
It's a super subjective award which often times makes it a bit useless. Things like golden boot in soccer seem much more meaningful to me because it's based on actual numbers.