Point entity
Point Entities are entities created at a specific position point on the grid. Some require a model to be selected for them in order to function fully.
Brush entity - the other type of entity, that consists of a set of brushes.
Logic entities
These entities are invisible entities that affect the game, creating or adding to various environmental and game controlling systems, such as lighting, AI managers, math counters and choreography.
Prop entities
Prop Entities, available only in the Source SDK[Clarify], are (usually) inanimate objects that use a model for their appearance and function. They can be static, dynamic, or physics. Some more specific props can even have functionality, such as a prop_door_rotating. Examples of prop entities include prop_detail, prop_dynamic and prop_ragdoll.
NPC entities
NPC entities, or "Non-Player Characters" entities, are computer controlled characters and creatures that can interact with the player(s) using their AI coding. NPCs generally fall into two categories, Friendly, NPCs that help, assist, or do not affect the player, and Hostile, NPCs that attack or negatively affect the player. Use ai_relationship to change this.
