Clash of Clans is one of the most popular mobile games in history, with hundreds of millions of downloads, the esports scene, and years of updates. It's a free "base defense" strategy game that lets players build - preparing their defenses or attack - trying to outsmart the enemy layout.
Building / defending is based on a few resources - gold, elixir, and eventually dark elixir. There are building for producing and storing those materials - upgrading and getting new ones will enlarge the available pool and add some idle income. The game will generously give you 2 builders at the beginning - and you might want to get even more, as constructions can take severe amounts of time. There are also many building and their upgrades oriented at building troops - from barracks and camp to structures summoning unique heroes. Yet, the most important one is Town Hall - its level affects available structures/upgrades and other game aspects.
Obviously, if you want to keep your resources from enemies, you'll need to add defense structures. Towers are the foundation - they differ in power, range, targeting, and area of effect. Also, to stop marching foes, you'll need to set p (and upgrade) walls around (and inside) base and possibly add some traps in-between.
The second main activity is attacking. You'll need to start with recruiting units - tanks, nukers, or multi-purpose brawlers. Then, find a reasonable target (preferably with lots of resources and weak defense), or just play PvE. You'll have control over deployment positions and timing, but once you send troops to battle - you can only sit and watch (and cast a spell sometimes). The best result is always a total obliteration. Still, this won't always be possible due to running time and defenses - you'll need to target as high destruction percentage as possible. Aside from standard units - lost when deployed - you'll be able to unlock upgradable heroes that not only could turn the tides of battle but are also immortal.
Clash of clans offers more than simply defending and attacking. There's a season challenge system, allowing you to get resources and cosmetic skins for your champions. The clan system is robust here - it enables sharing units and clan wars with many players involved or clan games to work toward a common goal.
The game is free and won't show you any ads. There's also no gacha system, but you might want to get some extra resources or premium currency - for example, to shield yourself from attacks.
