• Companion — ṣaḥābī (صحابی): met the Prophet ﷺ as a believer and died upon faith.
• Successor — tābiʿī (تابعی): not himself a Companion, but met a Companion as a believer.
• Meeting does not require eyesight; a blind person's encounter also counts.
Remember: Merely being a narrator or living in someone's era is not enough. Distinguish the two names using the encounter and faith conditions taught here.