Fan and Blowers

What a vague Question...

Fan -An apparatus with rotating blades that creates a current of air for cooling or ventilation.

Blowers - A person or thing that blows, typically a mechanical device for creating a current of air.

In short a fan has rotating blades like an airplane prop, many times a blower does too, but a blower may also refer to something that looks more like this:

A blower can be a traditional fan, but it can also be a "squirrel-cage" type design like pictured above. A fan cannot be a squirrel-cage type device, by definition.

"Fan -An apparatus with rotating blades that creates a current of air for cooling or ventilation.

Blowers - A person or thing that blows, typically a mechanical device for creating a current of air."

Exactly. And who would want a fanjob?

^{Okay, this'll get zapped}

There is no precise or universally agreed borderline, but blowers are generally higher outlet pressure than fans.

Fans may be axial (propeller) or centrifugal (squirrel cage).
Higher pressure squirrel cage units may be called blowers.
Positive displacement units (Roots, etc.) and regenerative turbines are usually called blowers.
Though the borderline is inexact, about 10 inches (250mm) water column is a reasonable dividing line, but not the only one.