(insert grain of salt - I never played wow but ..In GW2:) * Valor Point thing - There are so many different ways to get gear and such a wide variety of pieces that it's pretty much always fun to go after them. And they keep adding more.
Heroic Dungeons - The dungeon thing is fun in GW2 but could use some work. They've nerfed the money rewards you get form doing them - however, running them repeatedly gives you "tokens" of sorts which can be used for legendary weapons, some armor and weapons.
Tier Sets - There are cultural armor sets (3 of them) for each race - beyond that, there are a bazillion other armor pieces as I mentioned
Fast ground travel - Runes give you swiftness and things, but there are so many waypoints that traveling super swiftly isn't really an issue. Just jump to a place near where you want to be. There are no mounts.. but there are gliders. You can climb a mountain and float down, enjoying the view on the way.
Potions/Flasks: There's no healing potions per se - but there is a healing skill + traits that come from how your gear is setup. There are foods that provide constant regen. Healing isn't quite as critical as in any other MMO I've played. You need it - but unless it's during the RAID or something .. you'll probably be fine with whatever is fun for you.
Darkmoon Fair: I'm not sure what that is.. but yes, GW2 has a super adventure box which rolls around every now and then. There are tons of videos on yt about it. It's pretty cool and retro-ish.
Importance of Crafting: Legendary weapons can be crafted and you'll need to level up your crafting skill to do that. It can be lots of fun if you're into crafting - and you can make good money on the trading post. Personally, I don't do much of it.
Re-Specs possible: You can constantly respec with new sigils + armor + multiple characters (which you'd probably end up wanting). Each class has a variety of weapons that can be switched out to work with different builds.
Part 2:
Story Mode is when a player first arrives at a dungeon - lower leveled - and ready to hear about why that dungeon is there in the first place. Exploration mode has more paths to choose from, is more challenging, and provides the "tokens" which I mentioned before. Each path has it's sort of story that goes with it too. It all ties in together.
Levels: You can reach level 80 - then if you have the expansion you can "level up" to 163 (it's not really a level per se.. but a mastery level). You also have world versus world levels.. pvp levels.. crafting levels.. a lvl2 in a lvl 40 dungeon? haven't seen that.. how'd he live?
Summon people: Elementals can summon golems and what-not.. necros can summon dead stuff.. but summoning people? Not really.
Crystals thing: In GW2 - Gems. You absolutely don't have to use gems - ever. This is not a pay 2 win game. For the most part - the things you buy with gems are aesthetic or time savers (such as a mining pick which never breaks).
Other players, please feel free to embellish and/or correct me. I've done my best! Good luck!