You are partially correct because you say that "necesita" is a verb. However, verbs are gender neutral. It's the subject pronouns that have gender, and the endings of the verbs reflect that gender.
Thus, necesito = "I need," necesitas = singular familiar "you need," necesita = he, she, it, or you (singular formal) need, necesitamos = we need, necesitáis = you (plural familiar) need, and necesitan = they or you (plural formal) need. Incidentally, "necesitar" is a regular verb.