An explicit equation is an equation used to find a term in a sequence without using the any previous terms. For example, if I have the set of numbers 1, 3, 5, 7, 9, my explicit equation is F(n)=2(n-1)+1. If I plug 1 in for n, I get F(1)= 2(0)+1, which is 1, my first term.
Hope this made sense.