A compatriot is a person from the same country as you. Don't confuse it with patriot, which means someone with notable love for his country.
The word compatriot is often used to suggest an automatic sense of friendship. All compatriots are assumed to be chummy with each other — though, in fact, there's nothing in the dictionary definition to suggest this. Compatriots may — and often do — loathe each other, as countless civil wars have demonstrated.