Users should not have to look up the meaning of any words, phrases, or terminology used on your site. For example, the use of any abbreviations or acronyms should be limited and you should never assume users will know what they mean. If there are any features or concepts that the common user would not easily understand, you should take care to provide the necessary explanations and definitions directly on the site. The consequence of users not understanding important information on your site, is they might seek elsewhere to carry out whatever tasks they're trying to complete.