Spawning

Spawning is the in-game creation of an entity, for instance a player character, a non-player character (NPC), or an item. Respawning is the recreation of a player, NPC, monster, or item after its death, destruction, or use. In RuneScape 2, respawn rates depend on the number of players on the server with faster respawns for a higher populated server. It is not yet verified if this applies to RuneScape Classic as well.

Player Characters
Spawning of players occurs at the beginning of the game on Tutorial island. Players that log out remain in the same location upon login, so technically, logging in is not a respawn. Players respawn in Lumbridge upon death, typically at the hands of an NPC, player killers in the Wilderness, or from losing a duel.

Non-Player Characters
Non-player characters will respawn upon their death at a certain location after a certain amount of time. This allows for effective combat training because, if there are enough NPCs in a location, the first will have respawned before the last is killed and thus the player can continuously train without having to wait for an NPC to respawn.

Items
Certain items occur at set locations in the game, called item spawns. When a player picks up one of these items, it will respawn in the same place after a set time period. Item spawns include such items as runes, low-levelled weapons, low-levelled armour, food, logs, bones and big bones, and various other items. Picking up these items and either world switching or waiting for said item to respawn is a very good money making method for low leveled players.

Other
Other objects in the game can also respawn, such as trees, mining rocks, or flax plants. Unlike RuneScape 2, fishing spots cannot move or disappear and so do not respawn.