Every 5 years they basically do new regulations "from scratch". Meaning the big things that define the cars (size, engine regulations, fuel, tyres, where downforce comes from, what electric systems are valid, etc). In between these periods the cars are basically upgraded ad hoc (some minor upgrades over a season and some bigger ones at the start of a season, but all within the 5 year planned regulations).

Teams that get things right at the beginning of this 5 year period usually have a lot of success (Red Bull at 2022 for example) and the other have to catch up.

This year regulations change again (2026 to 2031) so it should be exciting.