It could be for several reasons, the most common being misspelling and/or using foul or offensive language. You shouldn't use text style typing when asking a question or answering either. Hope this helps, welcome aboard.

 In addition to what tiggersmom has said, it i also possible that an answer is disapproved for duplicate content.  This seems to mean that the content of your answer has been cut and pasted from another source and is not in your own words, so be careful of plagiarism.  And welcome to this community.  It takes all some time to understand the workings here, but many people will help if you ask.  So I am glad you asked.

 You asked this question and you succeeded :)

 Go to ask and then to the right catagory that you want and then ask your question.

 It's because the moderators/modifiers have biases and/or stupidities.Just go with it. Blurt to an excess as insurance.