I'm not sure if this is the correct industry term, but 'wongarsu used it and explained it here[0], so I just picked it up. Basically, it's forcing you to wait hours to do the next step in the game - so that you'll start scheduling your day around the game.
Time gating is basically any kind of mechanic that requires real-world time to pass before progression can happen.
Mobile games use time gating for "lives" or "energy" or something so you can only play so much then you have to wait. Then they try and get you to spend real money to circumvent the time gate.
MMOs use time gating to slow player progression, with mechanics where you can only earn certain rewards once per day or once per week or something. It slows players becoming too powerful too quickly, or from completing their collections too quickly or from grinding the new rare drop in the first week.
This type of stuff is even creeping into other types of games, unfortunately. Especially with every game nowadays being an online game, even the single player ones.
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[0] - https://news.ycombinator.com/item?id=26076702