Game mechanisms or game mechanics simply refer to a specific element or type of gameplay.
Let's get technical!
Game mechanics make up the skeletal bone structure of a game whether it's tile placement, area control, card drafting, set collection, cooperative, dice rolling, simultaneous action selection or worker placement - the list goes on.
You won't find any of these mechanics in the rulebooks but rather in the depths of game blogs like BoardGameGeek (BGG). If you have played board games in the past, you already have mechanisms that you like and dislike without even knowing it.
A good game mechanic can draw up interest even if you don't know how to play. If game like Monopoly Deal you might like other "set collection" games like 7 Wonders Duel(2015) or Terraforming Mars (2016).
Understanding popular mechanics can put you in the right direction when you are designing a game. "Singing" is one of the least popular game mechanics so obviously Big Breakfast did not include any singing aspects. Singing is great, but not when it is a central component of a board game(or if you sound bad).
BGG has a good list of the most poplular(and least popular) mechanics. Find your favourite board game on BGG and scroll down to mechanisms - you can see all of the mechanisms that are part of that game and you can click to see other games with the same mechanics.
#1 game Mechanism on BGG is... dice rolling. I guess people love rolling dice? I love rolling dice!
After researching poplular mechanisms, the goal was to incorporate them into our game framework. From BGG's most popular game mechanics, we were able to incorporate 3 of the top 6 into Big Breakfast which include: set collection, card drafting and hand management.