Mechanically, basic COH/COV gameplay is third person follow camera or first person camera (user's choice), using mouse and/or keyboard to target, keyboard and/or mouse to move, and mouse and/or keyboard to activate superpowers (spells, whatever). There's a chat box for finding teams, communicating, etc., and you also use the chat box to enter certain game commands as well as "emotes" (making your character do something on screen like make a "thumbs up" gesture, hold up a lit torch, sit on the ground, or dance the funky chicken).
Procedurally, characters generally visit contacts (mission brokers, whatever), accept missions from those contacts, travel across the city, and enter instanced maps to accomplish their missions. (There are some missions that are not accomplished on instanced maps, but rather by "counting defeats" on the streets or the dreaded "visiting another contact just to be told to go somewhere else.") "New" contacts (those for whom you have accomplished zero up to a couple missions; it varies) need to be visited in person; "older" contacts (those for whom you have accomplished more than a couple missions; again, it varies) give you their "cell phone" number so you don't have to travel back to them.
Defeating enemies is also how you reap the game's currency -- Influence (COH) or Infamy (COV) -- to spend on enhancing your powers or inspiring yourself to temporary greatness (with the game's only "loot"*) or on making costume alterations (as you reach higher character levels, you get the opportunity to unlock up to 4 costumes, as well as capes and emanating auras).
* Enhancements look like little "medallions" that you slot into your power menu, and as you level you not only get new powers but new slots into which to put enhancements (you choose which powers get additional slots). You can buy Enhancements from in-game "stores," and they also drop as loot from defeated enemies. Inspirations are temporary improvements to some aspect of your character's performance that you activate when you need them. You can buy these from contacts, but they also drop as loot.
Teaming is optional though definitely recommended to get the most out of your game. Teams can range in size from two to eight, and be made up of any combination of the different character archetypes... though a lot of players have favorite teammate types. Teams vary in quality, of course, but that's the chance you take. I tend to get pretty lucky finding good teams, though of the bad ones I have found, some approach legendarily bad. But you can always quit a team that you don't like and you can always ignore players that are being rude. A good team can get you through a rough patch (and there are a few), and at high levels a team is very helpful in defeating certain very powerful enemies.
Both the COH milieu (Paragon City) and the COV milieu (the Rogue Isles) are divvied up into "zones" that are generally demarcated by enemy level. For example, Paragon City has two "starting character" zones, where the enemies range from levels 1-6, and one "populated by giant monsters" zone, where every single enemy is capable of taking on an 8-man team of the highest level characters in the game with a fairly good chance of defeating at least one or two of them.
You don't need both Heroes and Villains to get started; one or the other is definitely sufficient.
COH has much more of the "bright, shining hero" feel (citizens on the street will almost always try to find you and thank you for saving them from a mugging, for instance), but the missions and contacts are typically spread widely apart, as Paragon City is a large sprawling metropolis. There are plusses and minuses to this: on the one hand, it can take a while to get places, but on the other hand you frequently have the option of "street hunting" along the way. (If you're not feeling "super" lately, go to a lower level zone and bust some bad guys that you've long out-leveled; laughing at bad guys you once feared goes a long way to impressing your progress upon you.)
COV has much more of the "grim, gritty" feel, although I view the characters as meant more to be sneeringly nasty than out-and-out evil (must maintain our Teen rating, after all). The Rogue Isles don't feel nearly as large as Paragon City, and it certainly feels to me like there's a lot less travel time, for better or worse ("street hunting" is still an option, of course). In every zone after the "starting character" zone (there is only one in COV), you are introduced to a "newspaper broker" who, once visited, gives you the power to accept "randomized" missions from the Rogue Isles newspaper, so as long as your level is "correct" for the zone you're in, you'll never lack for an instanced mission to run. (This feature has been promised for COH, but is probably not coming for a while.)
There are zones where both heroes and villains can meet each other; one is neutral territory (sort of a dance club), but the others are player-versus-player (PVP). PVP is ONLY possible in the three (soon to be four) designated PVP zones. (One of the zones is actually free-for-all.) The nigh-invisible "stalker" villain archetype is currently the undisputed king of PVP. Apart from the PVP zones and the dance club, heroes and villains don't interact; they can't even trade with each other in the dance club (though the dance club is the only place they can form a team; the developers showcased some hero+villain cooperative missions back in February and promise more opportunities like that are forthcoming).
Does that answer your questions?
