FNaF World's story is just as crazy as its cast of characters permits. Basically you play more than 40 characters from the FNaF universe as they embark on an adventure through a fantasy world shared with other evil creatures. Nothing makes any sense, but nor does the game try very hard in this respect.
FNaF World's gameplay is the one typically found in the JRPG genre. In other words, you manage a group of characters, level them up, equip them with different objects, etc. The battles, just like how they used to be in JRPGs from the 90s, are random and annoying; and they're turn-based.
FNaF World is an entertaining but improvable JRPG. Fans of the Five Nights at Freddy's saga will undoubtedly like the game, but it only takes half an hour of playing to realize that it's an outdated title in every respect.