recursive method to comput psF(n)

[Mcody2]

can someone explain to me how recursive methods work
we went over it in class but i was not listening and now i'am to scared to tell the teacher. can't focus for more than 50 mins at a time
how can you use a method within it self

static int psF(int n) {
if(n<2)
return n;
else
return 2*psF(n-1)+psF(n-2);
}

how can he use a method call with in a method