En snubbe is a way to say 'guy' in Swedish, but there are a few nuances you should be aware of.
There's often a strong connotation of typically masculine behaviour: if you describe someone as en riktig snubbe, it's like saying they're 'a real guy's guy', 'man's man' or 'bloke' in British English.
But you can also use it as a synonym for kille, to refer to any male person even without these connotations. It's very colloquial and could be translated as 'guy', 'fellow' or 'dude'. There's a big overlap with the term kille, but in general a kille would be under 30 whereas a snubbe could be older.
And there's no implication of positivity or negativity: you could describe someone as en skön snubbe (a good guy) or en konstig snubbe (a strange guy), for example.
So where did this word come from? It's a relatively recent slang term and originated around the 1940s-1950s as a Stockholm variation of gubbe, which is used to refer to both young and old men and boys. It might even be a portmanteau of snäsig gubbe (literally something like 'grumpy man').
Fun fact: The Swedish version of the Disney film The Aristocats translates the song Everybody wants to be a cat to Alla snubbar vill ju vara katt (all the dudes want to be cats).
Jag känner en snubbe som kan hjälpa dig
I know a guy who can help you
Det är inte alltid lätt att vara snubbe
It's not always easy being a guy