Actually two mechanics that are very often paired, Hand management/Set collection requires that the items in the players 'hand' (typically cards) are collected throughout the game and there is a limited number that can be in that hand at all times (thus the management.) These items can be used when collected in the correct patterns to activate abilities in the game. Often cards can be played in multiple ways and depending on board positions and other cards played deciding what is optimal is often a difficult decision. These mechanics are also often secondary to another mechanic.
An example of this is the Collaborative game Pandemic, which requires the players to think critically about their decisions and to work as a team to solve the problem of the spreading diseases.