Masala is mixture of herbal spices used in cooking food to make it tasty. Masala is in paste or powder form mixture including garlic, ginger, chili, cardamon, turmeric coriander cumin, etc.
These spices give nice flavor to the dish when added in small and measured quality. When these spices are blend together instead of putting all one by one to the food, that becomes Masala mix. Masala can be preserved and used when wanted.
Masala sometime refer to spicy gravy food item also.