First things first, your equation is mistyped, since you have oxygen on the reactans' side, but not on the products' side. The correct balanced equation for this reaction is this one
8H2(g)+S8(g)→8H2S(g)
Now for the mole ratio between H2 and H2S. What a mole ratio tells is in what proportion the two compounds will be when this reaction takes place. Notice that the coefficients in front of H2 and H2S are both equal to 8.
This is what a 1:1 mole ratio is - the number of moles of one compounds is identical to the number of moles of another compound.
What that means is that regardless of how many moles of H2 you have, the number of moles of H2S produced will always be equal to the number of moles of H2 that react.
If you have, for example, 0.100 moles of H2 that react, you'll automatically have 0.100 moles of H2S that are produced.
By comparison, the mole ratio between H2 and S8 is 8:1. Regardless of how many moles of S8 react, you'll always have 8 times more moles of H2 that are needed to react.
In essence, a mole ratio tells you the proportion in which the species involved in a reaction must be at all times.
So, if I give you 0.0250 moles of H2 and ask you to tell me the number of moles of S8 you need to react with this amount of hydrogen and the number of moles of H2S you produce, use the mole ratios.
0.0250 molesH2⋅1 moleS88 molesH2=0.00313 moles S8
0.0250 molesH2⋅1 moleH21 moleH2S=0.0250 moles H2S
