When you kill a creature, you need to wait some time until this creature is generated by the server. Players will refer to respawn as the delay that you have to wait until the creature reappears, the fact of the creature reappearing, or the place where some creature respawns.
The time of respawn will take longer when your server has fewer people online. An advantage of hunting when many are online is the speed the creatures will respawn, thus giving you more experience. However, with more people online there is a better chance that your hunting spot will be claimed or public spots will be crowded.
Some tips for a better respawning
- Do not stay at the place where creatures have to respawn, player presence interrupts respawning (go some squares away and wait there fishing, eating...). This is not true for creatures which are unblockable.
- When training with creatures, try to go to a place where you won't disturb respawns of other creatures and other players hunting.