When one takes a well deserved nap.

3 hours of sleep or less

Napping is when rest is used for the form of entertainment.

A time of relaxation, not necessarily a sleep. Just a time where you can lie down and recuperate.

To (intentionally) sleep for a short period of time; doze

"A day without a nap is like a cupcake without frosting."
- Terri Guillemets

Non Aggression Pact.

A pro re nata session of sleep. Can last as little as 10 minutes (powernap), to 3-4 hours. Not recommended for the ambitious personality, and usually frowned upon by semper fidelis types. Naps are sometimes instituted in some kindgergarten classes. Excessively long daytime naps may contribute to insomnia.