What is the main religion of your world? 

Main can be either the most powerful one or the most popular one.  

Worship who or what?

(go to #28 Holidays for questions about that)

Are there foods that are not to be eaten because of the religion? (related to #16 Food)

Are there certain ways to dress because of the religion? (related to #14 Fashion)

Are there laws influenced by the religion? Does the government have a say in those religion influenced laws? For or against it? Perhaps, in conflict with the religion? (related to #8 Government)

Religion is another one of those like the climate which can affect many aspects of your races/species lives. Food, fashion, language, education, government body itself, governing laws, holidays, recipes...the list goes on and on. Oh, housing styles, too.

Religion is a very powerful element in fictional worlds. If it is the center of your world, recall our own Earth here and how religion has affected many people's lives.