Auto-battler
Also said as Auto chess, Autobattler
You buy units from a shop and place them, then the battle fights itself while you watch. It promises strategy without any need for fast hands: the whole game is what you did before the fight.
Your spare gold is always a question: spend now or save for interest. Three copies of a unit merge into a stronger one, so an ordinary shop becomes a hunt for one particular card.
Say it
“Auto-battler economy: five gold a round, plus one for every ten saved, up to five. Reroll costs two, and three copies merge to two-star, with about double health and damage.”
Where you’ve seen it
Dota Auto Chess, a 2019 Dota 2 mod by Drodo Studio, set the rules: eight players, a random shared shop, and three copies merge into a two-star unit. Teamfight Tactics and Dota Underlords followed the same year.
Not to be confused with tower defence
A tower defence is against set waves and you can act during them. An auto-battler usually pits you against other players' boards, and you can only watch.