An idealist is someone who envisions an ideal world rather than the real one. Some people consider idealists to be naive, impractical, and out of touch with reality. Idealists think that striving for perfection makes the world a better place.
The main root of idealist is "ideal," which comes from the Latin word idea. As an idealist, you think everyone should act in the best interest of the group. Ideally, everyone would agree with you, but the unfortunate reality is that lots of people act solely in their own self-interest. Words that are related to idealist include "idealize," "idealism," and "ideally."