I'm just learning to cook, and when I use wine in a recipe.....?

Alcohol not only evaporates without heat, but the majority also burns off during the cooking process. How much remains in the dish depends on the cooking method and amount of cooking time. Those bourbon-soaked fruitcakes would have to turn into bricks before the alcohol evaporates. A bottle of Guinness in a long-simmered stew is not going to leave a significantly measurable alcohol residue, but will add a rich, robust flavor. A quick flambe may not burn off all the alcohol, whereas a wine reduction sauce will leave little if any alcohol content. Heat and time are the keys. Obviously, uncooked foods with alcohol will retain the most alcohol.