brake fluid absorbs moisture thus brings the boiling point of your brake fluid down to a much lower temperature. if your brake fluid reaches this temperature you can loose your brakes temporally. also the moisture in the fluid will cause highly unwanted corrosion of internal parts of your brake system.
Be sure the cap is on tight, brake fluid absorbs moisture quickly if the container is left open.
If it looks like a smaller version of the brake cylinder container it is the hydraulic clutch reservoir ( assuming you have a manual ) and you will fill it with brake fluid.
most any brake fluid which is DOT approved should be fine. Be sure to use a new, unopened container.
brake fluid container right side behind battery.
Depending on the vehicle, under the hood there is a container that is labeled Brake Fluid. That is where a person measures the amount of brake fluid left, and with a funnel adds the appropriate amount.
What could be wrong is your brake fluid is low in the Brake fluid container, could be a knot (kink) in the pipes or it needs to be bled in.
Do not drive the car. Have it towed to a repair shop and have the brake fluid changed.
there is too much in the container If you filled the resevior with brake fluid PRIOR to replacing any of the brake linings, it will cause the fluid to "backflow" into the resevior, thus it will overflow and leak from the cap.
The brake fluid reservoir in a 1991 Jeep Cherokee is located on the master cylinder. To add fluid, unscrew the cap and fill to the appropriate level with the appropriate brake fluid, more than likely dot 3.
The clutch fluid and the brake fluid can both be filled in the brake fluid reservoir.
dot 3. nothing fancy always add brake fluid from a sealed container. It absorbs moisture.
Brake fluid should have low freezing point