Palestinians are the people of Palestine, formally the State of Palestine—a de jure sovereign state recognized by 140+ UN members, with de facto partial control over:
The Palestine Liberation Organization (PLO) is the internationally recognized representative. The Palestinian Authority (PA) administers parts of the West Bank (Areas A/B) under Oslo Accords; Hamas governs Gaza since 2007.
Palestinians also form a large diaspora (refugees and descendants in Jordan, Lebanon, Syria, Chile, US, Europe, Gulf).
Key distinction: "Palestinian" is a national/ethnic identity; "Palestine" is the territorial entity. Not all residents of historic Palestine identify as Palestinian (e.g., Israeli settlers), and not all Palestinians live in Palestine.