How does damage work

Ezreal's Q does 35 damage +110% AD and +40% AP

is that 35 physical or magic damage?

If you read the spell, it should tell you the type of damage it deals. Ezreal's Q scales with both AD and AP, so if you build a BF sword and a Blasting Wand, both will make his Q do more damage but the damage type dealt will be physical. The 35 base damage is also physical because the damage type of the spell is physical.