What is the difference between the Companions (Sahabah) and the Successors (Tabi'in), and is everyone who lived in the Arabian Peninsula during the time of the Prophet, may Allah bless him and grant him peace, considered a Companion, even if they did not see him?

A Companion (Sahabi) is one who met the Prophet Muhammad, peace and blessings be upon him, believing in him, and died upon Islam, even if an apostasy intervened and then he returned to Islam. As for the Successor (Tabi'i), he is one who did not meet the Prophet, but rather met his Companions, or met him but did not believe in him until after his death. Therefore, companionship requires faith, direct meeting with the Prophet, and dying upon the religion of Islam.