2002 Dodge Durango ,Driver side brake light
The most likely cause of this is that the bulb has burned out. Unless you have upgraded the tail lights to use LEDs then they will be standard incandescent bulbs which burn out and need replacement every once and awhile. They are extremely cheap and generally easy to install with basic tools.
So replace the bulb first, if it still doesn't work then it could corrosion on the electrical contacts for the bulb, cleaning the contacts may resolve it. Otherwise, it's going to be an electrical problem of some kind, the wiring to the tail-light assembly has a fault or the assembly itself is broken.
But it's probably the bulb.