者 (zhě) is a productive nominalizer meaning "one who…" — it turns verbs/adjectives into the person/thing that does or has that quality:
成功 (succeed) →
成功者 (achiever);
强 (strong) →
强者 (the strong);
学习 (study) →
学习者 (learner). Slightly literary register; conversational alternatives are
成功的人 or
成功人士.
