Once registered, you receive a trademark certificate confirming ownership. You can begin using the ® symbol in connection with the mark in the jurisdictions where it is registered.
Post-registration, the trademark must be maintained. In the US, a Declaration of Use must be filed between the 5th and 6th year after registration. In all jurisdictions, the trademark must be renewed every 10 years and must be put to genuine use in commerce to avoid non-use cancellation (five years in most jurisdictions).
The registration also gives you active enforcement rights: you can oppose similar trademark applications, send cease and desist letters, report infringement on platforms such as Amazon, and pursue legal action against infringers.