"OnlyFap" is often the title of adult-themed parody games or visual novels found on platforms like Itch.io, Patreon, or Steam. "Fitness Baby" likely refers to a specific character or expansion pack within that game.
Titles like "Free Download (Uncensored)" are very common hooks used by third-party sites to distribute malware, adware, or trojans . If you found this on a forum or a file-sharing site, there is a high probability the file is unsafe. A few tips if you're looking for the actual content: OnlyFap: Fitness Baby Free Download (Uncensored)
However, based on the phrasing, this looks like it could be one of two things: "OnlyFap" is often the title of adult-themed parody