Idealism means believing strongly in ideals — the best, most perfect way things could be — and wanting to work toward that, even when it's difficult or not fully possible in real life. It can be a compliment, describing someone hopeful who wants to make things better, or a gentle criticism, suggesting someone isn't being realistic enough about how the world actually works. In philosophy, idealism is also a more technical idea: that reality is mainly made up of ideas or minds, rather than physical matter.