A Japanese word, gacha refers to a system of dispensing prizes in a toy vending machine. For the purposes of a mobile game, it is a mechanism to give randomised virtual items for progress in the game, or if you choose to spend real-life money to give further rewards. Rarer items drop less frequently than common ones, like in Dungeons & Dragons treasure tables.
Instead of loot boxes, chests or brown paper bags, in Mr Football this is represented as foil card packs like the ones you get at the shops. The cards inside are not made of paper, but they can be used to play the game as if they are real footballers and they can be upgraded, equipped and levelled up as in tabletop role-playing games.
An important aspect of the Mr Football gacha system is that not every player is available in every kind of pack. The list of those players who are in packs is called the draft pool; the minority who are not in the draft pool can be purchased with soft currencies or earned in events.
Card packs come in five broad types, listed below. Some have sub-types as well.