Modifiers are automatic operations that affect an object in a non-destructive way.
Modifiers are used to modify objects non-destructively until Applied.
There are four groups of Modifiers:
Modifiers in the Modify group act simpler than those in the Deform group without directly affecting the objects shape, rather than affecting some data.
The Generate group of modifiers directly modifies the shape and/or Topology of an object.
The modifiers in the Deform group affect only the shape of an object without changing its Topology. These modifiers are often available for types of objects other than Mesh objects such as curves, text objects, and so on.
Simulate modifiers are mainly used (except for the Explode, Ocean, and Particle Instance modifiers) to define where in the Modifier Stack a physics simulation takes place.
Blender's Modifiers are listed in the manual.
- Modifier Stack
Blender's modifier system is handled in a "stack" that can be thought of as a sort of assembly line. Each modifier is a process that is fed the outputted object of the modifier above it and in turn modifies and outputs that object to the next modifier in line or, if no more modifiers exist below it, as the final result.