EVs and IVs are really important.
To explain EVs simply, for every 4 EVs in a stat you gain 1 point in that stat. The maximum amount of EVs you can have in a stat is 252. You can max out 2 stats and put the remaining 4 in another one.
So in total you have 508 useful EVs available(you actually have 510 but the last 2 don't make a difference).
IVs are a bit more complicated. They are like Pokemon genes. They determine your Pokemon's stats and cannot be changed unlike EVs.
HP IVs are calculated differently from the rest. These two formulas are used to calculate the IVs:
Aside from determining stats, they also determine what kind of hidden power your Pokemon will have.
>The last binary digit for each stat sets the move's Type, and the second-to-last digit sets the move's Power.
Sources: Knowledge and Bulbapedia page for IVs and EVs
Hope I helped.