Vegan indicates that no animal products or compounds of animal origin are incorporated.
Definition
A Vegan diet is one where a conscientious effort is made to eliminate animal products and by-products from one's food. This attempt to eliminate anything of animal origin is not limited solely to meats from animals, but also excludes dairy products (i.e. milk and cheese), and other animal proteins/compounds that are harvested for use as stabilizers in other foods (i.e. casein, gelatin).
If you are using this tag on a question, be sure to follow proper semantic guidelines (i.e. do not use the tag to cover a concept like vegetarian, which is less exclusive, or to cover lactose-intolerance).
For general questions about vegan lifestyle, see our sister site Veganism & Vegetarianism Stack Exchange.
Answering Vegan Questions
Certain constraints typically arise in vegan questions. In order to give a valuable response to one of these questions, try to keep these elements in mind:
Vegan questions may often involve requesting a substitution, or clarification of whether some ingredient or product is vegan or not. They can also extend to cover resources like cookbooks. Try to provide an actionable answer in any case; while many answers may exist, begin with a responsive answer, then add information to be more comprehensive
Successful answers responding to a vegan tag should try (first) to gather what the question is asking for, and (second) to observe any restrictions included in the question.
If a question seems to require (but doesn't address) context or a basis for explaining the constraints around planning a meal, be sure to include this as it may make your answer more helpful
Etiquette
The same rules apply to this tag as any other tag. Unwarranted criticism or "shouting down" the question, such as those along the lines of "why would you want to [use not-meat in place of meat]?" will not be tolerated. However, if there is an actual structural issue that would arise, please include this as a comment directly responding to the question so that it can be addressed by the asker.