What vegans do not eat are any foods that contains animals or is a by product of animals. Such as all meat, dairy (and it's byproducts such as whey & butter), sea animals, eggs, honey.
For detailed information:
Animal Ingredient List A-Z
Animal Ingredients
Criteria For Vegan Food
Questions About Food Ingredients
Which E-numbers and additives are from animal origin
Stumbling Blocks
Hidden Non-Vegetarian Ingredients