You will gain access to Premium and Business features. The contents of your account will become part of the Business account and your Business will control (and own) your account content, subject to the Terms of Service. You will not be able to remove your content without the Business' approval.
If you have pre-existing content in your account that you do not want transferred to the Business, you should join the Business using a different email address. If you used your work email for your pre-existing account, you can update the email address on that account to an email address that will not be associated with the Business.