There are 3 main components to design video games:
– The core gameplay: basically, the main direct actions that the player will be able to perform. Like jumping or selecting an item and choosing an action.
– The level design: it’s about level building, the learning curve and the difficulty curve.
– The meta gameplay: it’s everything else. Actually, it’s everything that uses core gameplay and level design to build a whole experience for the player.
If we take World of Warcraft for instance, the main two core gameplay mechanics are to walk and to select a target and apply an action to it (attack a monster, pick up plants, crafting, fish…). The level design is the world the player evolves into, the level progression for multiple traits and the general progression of the player. Finally, the meta gameplay is represented by the class of the player, the gold that helps him buy stuff, the multiple level systems, the missions, the achievements…
One other great example is Cookie Clicker (inspired from Candy Box). The goal is just to get cookies, but a lot of surrounding elements allow the player to get them differently.