A friend of mine gave this to me as a challenge. I almost have no clue what I'm supposed to do

he says "Solve for the following equation for f(x)"

$\displaystyle f(x) = x + \lambda \int_0^1 f(\xi) \,\,d \xi$

can anyone tell me what type of problem this is so I can do a bit of research on my own? My understanding of calculus only spans from Calc I to Calc II