ode to joy:

Fake is a term used to describe or imply that something is not real or that it is false.

Examples and applications include:

Dramatic portrayals 

A film or play may show fictional events, actors typically show fake emotions, and fake objects (e.g., props) and fake houses (movie sets) are used

Professional wrestling entertainment (e.g., WWE)

Fiction 

Novels create made-up characters and settings

Fictional examples used as case studies in law, medicine, etc.
Facebook pictures are often not representative of the actual person, some users have cross-gender avatars.

An insult used to describe a person who lies, pretends to be something they are not (e.g., a poseur), does not have an opinion of their own or pretends to like things he or she does not.

Deception 

A forgery (a false document or picture)

A counterfeit (of an object)

A decoy (e.g., a cannon-shaped object made of wood which is designed to fool the enemy)

When a singer lip syncs to a recording during a purportedly live concert

A charlatan (a person who falsely purports to be a doctor)

The same purpose (partly or fully) as the real thing

Meat analogue (e.g., tofu hot dogs)

Imitation fur

Artificial leather

Fake guns used in a bank robbery; for this reason realistic-looking fake guns are often prohibited

Reasons for using a fake object instead of the real thing include: 

The real thing does not exist, including: 

A reconstruction of a historical object made based on historical accounts or speculation

A fantasy object (e.g., a "laser blaster" held by an actor in a sci-fi film)

A fake version of an object may:

be more easily available (e.g., artificial vanilla flavour does not require vanilla beans)

be less expensive (e.g., a glass rhinestone in costume jewellery, vinyl imitation leather, etc.)

be at less of a risk of damage or theft (e.g., when a replica of an Egyptian tomb treasure is displayed in a museum)

be less dangerous (e.g. a toy weapon, or a weapon prop)

be less heavy (e.g., an imitation oak beam which is hollow, but covered with a thin layer of veneer)

not require an animal to be killed (meat analogue, imitation fur, imitation ivory piano keys)

be legal while the real thing is illegal (e.g., a replica of an AK-47 designed for the US civilian market which can only fire in semi-automatic mode)

not require a license (e.g., a replica of a flintlock musket which cannot chamber or fire ammunition)

Decoys used as military targets or to deceive the enemy (e.g., dummy tanks made of wood) are much less expensive and lighter than the real thing.

As a version of 'not really'- exclaimed when something is said or done, but no offence meant by it. Currently peculiar to England (2010).