Snack bar usually refers to an inexpensive food counter that is part of a permanent structure where snack food and light meals are sold in Europe. However, Japanese snack bar is different. No one expects snack foods and most of the people do not order light meal while visiting the snack bar in Japan.
Snack bar in Japan is a hostess bar where you drink alcohol and chat with the hostess or you can enjoy karaoke too. The main difference between hostess club and snack bar is the price. Snack bar is cheaper than hostess club. Then, the reason is simple. There are a few ladies working at the at snack bars, sometimes just one lady who is the owner of the snack bar working inside the bar counter. Then, usually average age of the ladies are higher than hostess clubs.
Hostess clubs are located mainly in red light districts of principle cities but snack bars can be found much more residential areas. Therefore there are certain amount of female customers who visit the snack bars in Japan.
Snack bar is just called Snack in Japan. If you see this word, do not expect to visit it during the day and do not think to buy a snack food.