Arhat / Arahant – A Brahmā-bhūtaḥ (become-the-supreme / Dhamma-become) who radically transforms by detaching completely from samsara to fully experience Nirvāna.
Boddhisatva – In Mahayana Buddhism, one aspire to become Buddha. And to accumulate merit for it, bodhisattvas choose to remain within samsara to help beings.
Buddha – Neither god nor human, but a long-enlightened being who has attained / realized beyond (transcended) the unconscious traits that may make him a god or human. He sends his manifested appearance to teach on earth through direct presence of visionary experiences.
Enlightenment – a state that could be attained after perfecting human-ness
Gotama – portrayed as a human by Theravadins while divinized in Mahayana view, is a tranquil and compassionate figure who used his observation and intelligence to guide those who sought the Beyond.
According to Theravadins he was born as human but later he attained enlightenment that built him up as a boddhisatva, while for Mahayanists he perfected his human-ness and became the Buddha.
Saṃsāra – the conditioned world we live in
Seven factors of Enlightenment – 1) mindful alertness, 2) investigation of Dhamma, 3) vigor, 4) joy, 5) tranquility, 6) concentration, 7) equanimity.