In USA, a cafe is a light dish restaurant for breakfast or lunch and sometimes dessert. A snack bar is often a small establishment within another location. At a sports stadium or a bowling alley. They usually have very few seats and sell street style foods.

Depends on where you are, really. In certain countries, the two are almost the same. For instance, in France, a café serves alcohol, coffee and food, usually light food. In England, a pub usually does that. So, nowadays, the two are more or less synonymous.

A cafe is a place where people go to have coffee or tea. Sometimes light desserts or other foods are also sold. A snack bar, however, being that it is a type of bar would sell mostly alcoholic beverages and light foods (snacks).