Patch numbering and naming conventions are not standardised across the industry, but the vocabulary is close enough that knowing it saves you from being surprised by a Tuesday night patch that empties your inventory.
Patch numbers
The major.minor.build convention is common on PC, particularly for engines with public patch histories. Major increments are large content or system changes, minor increments are feature additions and balance work, and build increments are fixes.
Not all studios are consistent about this. Some increment the major number for anything user-visible, which makes the numbering much less informative. Reading the actual notes beats inferring from the number.
Hotfix
A hotfix is deployed outside the normal schedule, usually within hours or days, and it is almost always a fix for something that is actively broken. Server crashes, exploits, and items that can be duplicated are the usual causes.
The word carries a warning. If a hotfix is large enough to change balance, it usually means the release went out with a bug the studio did not catch, and there is a reasonable chance further changes follow once the cause is understood.
Major versus seasonal
In live-service games, a major update and a season are different things that often ship on the same day. The season is the frame: the reset, the battle pass, the reward track. The major update is the content that ships with it.
This matters because a player who wants the content does not necessarily need the season, and some studios eventually make seasonal content permanently available. If you are buying a game to play a specific new area, check whether that area is seasonal or permanent before assuming you need to finish it before it goes away.
Maintenance notices
A scheduled maintenance window means nothing is changing in your save, your items, or your progress. It is server work. Announcements that use maintenance language while also containing balance changes are unusual and worth reading carefully, because maintenance should never affect game state.