As adjectives, one is for singular words and the other for plural words: "higiene pessoal" = "personal hygiene"; "razões pessoais" = "personal reasons". Also "pessoal" can mean "personnel/staff" and can be used in a phrase like "Oi pessoal!" = "Hi guys!".
This sentence, can it also be like "não é pessoal" like in "it isn't people"? Let's say you think you see some people in the woods and then discovered that it wasn't. Could this sentence work for that purpose as well?