I can help with this!
Now, the game is known as a 'MOBA'. Which stands for Multiplayer Online Battle Arena.
The most common mode of play is '5 versus 5'.
It pits two teams up again each other. Each with 5 players on a team. And there is 3 lanes which players can control. The goal is to 'push' each lane, destroy the minions and towers owned by the other team, in each specific lane. All the way to the enemy's core/base.
The 5v5 map looks like this:
Now, the most common way people play is 2 players in the top lane, 2 in the bottom, and 1 in the middle lane. At times, all 5 players are against all 5 opponents, which are known as 'team fights'.
The 'roles' in the game are like most games. Warriors/Tanks, Supports/Healers, Assassins/Damage, and so on. A big part of the game is having a good team dynamic/chemistry so you all work well together class/role-wise.
Something you can include in a card, for example, is the phrase: 'You pushed your way to my core' or find a way to use the terms 'jungle' (when you build up your level/stats by defeating minions in the forest area of map, instead of fighting players). and 'gank/ganking' (when you ambush, basically).
Hope this bit of information helped!