Worms Armageddon is a turn-based, team-play game in which the player controls one of several worms on the screen. Each team includes eight worms, which can either be controlled by the computer, or your friends. This was a feature that, as far as I know, may have been only available in the PC version, but allowed you to create a team name and customize literally all of the features of the aforementioned team. This was particularly cool because you could also customize the terrain—something that this fairly simplistic game could have gotten tedious without.
The traditional objective of the game is to defeat the other team of worms with various weapons, ranging from traditional bazookas to, uh, creative weapons like the gas of a skunk. The whole scheme of weapons were not always available from the beginning, and were dependent on the weapon set chosen at the beginning of the game. Similarly, some weapons could be received from crates dropping on the terrain in mid-game.
Much like games nowadays, there was a "meta-game" for Worms Armageddon that focussed on adding different objectives (besides just killing the other team) along with plans of attack that were based wholly on a specific weapon or item. Two such metagames were Pro Roper, and Bazooka and Grenade.
I have gone ahead and found a place to play this online (as I try to do with all of the games I review), and have found an emulator here. It bears noting that the PC version is still undergoing updates as Team17 has hired two developers to continue this legacy. Along with being released for PC, which was where I played it, this game was also released for Dreamcast, Game Boy, Nintendo 64 and Playstation—making it a pretty widely released title. It was also released on Steam in 2012. You should check it out, it's usually pretty quick and basic and doesn't require much ramping up to get started.