Tikka means bits, or pieces, and masala is a blend of spices.
So, what is chicken tikka masala, exactly? Chicken tikka masala is chicken tikka,* chunks of chicken marinated in spices and yogurt, that is then baked in a clay tandoor oven, and served in a creamy, spiced masala sauce. The sauce is usually creamy and orange-coloured, although the particulars of the recipe can vary from kitchen to kitchen, and family to family.
The Indian tandoor oven dates back thousands of years, and the practice of marinating chicken or other meats in yogurt and spices (chicken tikka) goes back pretty far as well. But the addition of the orange, creamy, spicy masala to the chicken tikka is, curiously, not an Indian creation, ancient or otherwise!