If A Car Is Not Driven Does A Battery Loos Its Charge?

Yes. Modern cars have many small electrical loads like clocks, control units and computers that consume a small amount of power all the time. This will drain the battery given enough time.

And car batteries will also discharge themselves even if not connected to a car!

Depending on the car and its condition the battery might not have enough power to start the engine after 2 to 3 weeks, sooner if the battery is in bad shape or if there are lots of electronics.

You can buy inexpensive solar chargers that plug into a lighter socket and keep the battery charged if they are in good sunlight. Some car manufacturers actually use these to keep their cars batteries charged during shipment!