na-adjective
Describes ideas, policies, people, or movements that favor reform, innovation, or forward-looking change. Often used in political, social, or cultural contexts.
彼は進歩的な考え方を持っている。
He has progressive ideas.
その政党は進歩的な政策を掲げている。
That political party advocates progressive policies.
保守的 is the direct antonym, meaning conservative or resistant to change.
Compound of 進歩 (progress) + 的 (-like, -ish). The suffix 的 turns the noun into an adjectival noun meaning 'having the nature of progress'.