Speaking of clown replies.
Free to play means free, as in no cost. If I decide I want to play a Free to Play MMO, I might pick Lord of the Rings Online or DC Universe Online, both of which are free to play with no upfront cost.
If I want to play a Buy to Play MMO, then I might pick Guild Wars 2 or Elder Scrolls Online, which cost money upfront but once I own the game it’s free for me to play forever. I don’t have to shell out any more money unless I want to buy expansions or DLC.
Subscription MMOs usually require both an upfront purchase, and then a monthly subscription is also required.
Overwatch 1 is Buy to Play. Pay for the game once, then you don’t have to shell out money again for the title unless I want optional cosmetics. Overwatch 2 is going to be Free to Play, so there’s no upfront cost at all.