If you have never had a curry, then it is difficult to describe. It is similar in some ways to a very heavy stew. Like a stew, different curries have different ingredients. Some are mostly spices, while others include a tomato base. Tikka Masala is a chicken curry, and it has a creamy tomato yoghurt base.
Different people cook it different ways, and properly prepared it probably takes half a day to make.
This recipe, however, can be completed in far less time. Being a Texan-American, I've tried to find a substitute that tastes the same but requires less work. The taste of this recipe is usually delicious, but your results may vary. This recipe is significantly different that other recipes that you will see for tikka masala, but the taste is similar even though the ingredients are different. Garam Masala is a fancy word for spice mix.