Never played D1 or D2... Simple question here.

[paupsers]

I've tried finding this out through google but can't get any real clarification. Can someone explain how difficulty levels and acts work in Diablo?

After you beat the game on say, normal difficulty, you restart with the same character and try again on the next difficulty? And again with each difficulty level?

How many acts are there and how exactly do they work?

[paupsers]

And each difficulty has 4 acts?

What makes it "harder?" Do the enemies just have more health and do more damage? Any NEW enemies or new mechanics (besides the new spells you obtain)? How many levels should you expect to gain as you beat each difficulty?

[Orangetai420]

Oni covered basically everything.

Also, your life leech and mana leech from gear is less powerful in each difficulty.

Just a tip, if you happen to be playing on single player you can type /players x
where x is a number 1-8. it scales up monsters and exp.

For leveling I tend to stay in normal until 40, nightmare until 75, and hell 75+
You can get through the levels much earlier, its challenging and fun if you try to play straight through without farming bosses.

[Deleted]

Your elemental resistances also take a big hit when you go up in difficulty. If you have 0 in normal you'll have -40 in nightmare and -100 in hell, with mobs having more elemental enhancements in hell this can make it rather painful.

For example you could run into a unique monster that's lightning enhanced and fire enhanced. If you hit it you'll take lightning damage, if it dies it'll explode and do a lot of fire damage. That's one very painful combination if you're not keeping an eye on your resistances

[Deleted]

The acts are basically like areas, with an end boss. You progress through the story throu all of the acts, four in d3 and complete the game. I don't think we know exactly what level you're likely to be yet. Once you've completed the game on normal, you can rinse and repeat on hell, nightmare and inferno, so 4 difficulty settings total. The quests and story is the same, but it's worth noting that a large amount of the actual dungeon is random generated so it's different every play through except for the key quest areas and bosses.

Monsters have affixes which define what special abilities they do, on harder settings, in addition to all the other things getting harder like damage etc. you also get mobs with increasingly difficult combinations of abilities, so you may need to use a different strategy and build to survive.