Each online casino will have its own terms and conditions and your registration with the casino will not be accepted unless you agree to them. This is usually a simple task of checking a box upon the completion of the sign up, or sometimes you will be considered to have agreed to the terms and conditions by clicking on the 'submit' or 'signup' button.
Most terms and conditions include the basic house rules that you must abide by for continuous membership and also general rules regarding the use of bonuses and changing your personal details. They are not there to trick you into agreeing with anything that you would find unreasonable and are common among online casinos. Should you at any stage wish to discuss the terms and conditions then you are advised to speak with customer support of the online casino in question.