No there are no trivial details, and you don't need a mathematics major or category theory to understand what a functor is.
It's a pair of a type constructor F(a) and a map operation a -> b to get an F(b).
The two "non-trivial" details are the fact that the map operation has to respect identity, map(id) = id, and function composition: map(g ∘ f) = map(g) ∘ map(f)
None of those concepts is any difficult, nor requires any "math major" or non-trivial details, because the are not there.
It's a pair of a type constructor F(a) and a map operation a -> b to get an F(b).
The two "non-trivial" details are the fact that the map operation has to respect identity, map(id) = id, and function composition: map(g ∘ f) = map(g) ∘ map(f)
None of those concepts is any difficult, nor requires any "math major" or non-trivial details, because the are not there.