In a single hand you got a triple-barreled shotgun firing corrosive rounds that do 1000 points of damage whenever you score a good hit. 
Your friends are stood around you, wielding weaponry just as insane, healing you, sending decoys to confuse the enemy and throwing down turrets to bolster attack as those you are now pointing in the direction of the poor bastards.
But you're still getting confused.

It's something we didn't even realise we missed until we got back into the planet of Pandora and picked off our first dozen-or-so bullymongs (yes, that's really what they're called).
Fundamentally a first person shooter, Borderlands 2 brings back the fundamental RPG roots of the first. What this means is levelling up your own character, picking up larger, better, stronger firearms (or weaker, quicker-firing ones. Or ones where the elemental effect offsets any negatives concerning its ammo capacity. Or... you have the picture) and generally working with a hell of a lot of figures. Most of which virtually fly about the monitor as hell is unleashed on the denizens of the alien world.
But it's not a complicated sport and, actually, visits some pains to make it easier on players who might not want to spend half their time evaluating numbers (we do, for the report). Quick references appear on screen when looking at new items to show you at a glance in case you're looking at a much better or worse deal, and it normally makes things work that bit faster than they did in the very first match.

And that's basically the general feel of Borderlands 2: things work a bit faster. Somewhat better. Thoughts are more refined and thought through than before, from simple touches such as being able to talk to NPCs that bit more, to things like adding more variation to mission types (timed, failable, runs for example), as well as the addition of vehicles that can seat all players in coop.
Co-operative could be the chief meat here, never forget. Borderlands 2 is a much more interesting and fun game than the first one was when played by yourself, of this there may be no doubt. However, you'll become intensely aware of problems, of the trudge, of the bullet and the fetch quests - sponge supervisor battles when pootling around with nary another ear to natter at.

Throw in three other players - or two, or just one - and you have a captivating, fantastically moreish encounter. 

A conflict against among the aforementioned bullet sponges becomes a carefully orchestrated maelstrom of tactical thinking and renegade actions ("Why are you... DON'T GUNZERKER HOWEVER IT's A WASTE oh god he's Gunzerking..."). In a nutshell: co-operative play requires a great experience, though one certain to prove divisive when played alone, and turns it into a stupendously fun experience that may absolutely kill your leisure time with the power of at least four hundred bazillion guns.
Not necessarily, no. It's a big part of the main reason the score isn't quite as large as it might have been - you cannot discount the fact a lot of people will play the game alone, as well as lots of people may well get bored of what they're doing as a consequence. Similarly, a lot won't - a lot will love it. But it's still worth a chance if you're a vintage Billy No-Partners.
But in the event that you're an ordinary person, with web and friends, Borderlands 2 is essential things. Even though you tired of the very first match, the sequel offers more visual variety, interesting missions, likeable characters, puerile humour and weaponry-based strategies (firearms exploding like grenades on reload: a Superb Thing) to haul you in yet again.
Where Borderlands was 'sent out to die', Borderlands 2 has been sent out to kill. And it really does that. It'll easily become one of the finest games released all-year as well as the more we desire such tasty four-player coop, the more we think it's one of the top games this generation.