What is the difference between 概念 and 观念？
@Stan's comment is precise enough. To add my own interpret by deconstructing the words,

念 primarily means idea with a slight connotation of motivation/intention.

概 means brief; summary; abstract, hence 概念 is the abstract of the idea => concept.

观 is literally view, so 观念 is the idea as you see it => opinion; view.