Sheriff's Deputy

(Also known as a "Deputy Sheriff") is a police officer, but instead of working for a city, they work for the county that surrounds it and is employed by a "sheriff" instead of a "chief".

They're uniform is usually (at least on the US west coast) a tan/beige shirt with green or black pants with a star badge.

They patrol rural and suburban areas that don't have their own police departments. They sometimes go into big cities but only to bring prisoners from the city jail to the county jail.

They're usually the more chill cops but it always depends on where you live.

Example:
A cop working for the city of Los Angeles is a Los Angeles Police Officer

A cop working for Ventura County is a Ventura County Sheriff's Deputy
Usually in an emergency, the Sheriff has more authority, but a police officer and sheriff's deputy's everyday authority is the same

Self-Appointed Deputy Sheriff

The self-righteous asshole who insists on holding ALL communter traffic to 1 mph UNDER the posted limit

Look at that effin' Self-Appointed Deputy Sheriff up there, running 44mph in the left lane while granny's leading the parade in her K-car on the right!