I'm currently taking Modern Philosophy at my university, and we went over Berkeley and Locke in a span of ten minutes in order to get to Hume. As far as what they (Berkeley and Locke) thought about "ideas," how we acquire them or what role they play in relation to the mind or understanding, what is the main difference between them?
Locke, who was born 50 years before Berkeley, was an empiricist and maintained that all knowledge (and ideas) come to us through our experience of the physical world. He was specifically interested in denying the rationalist view that knowledge and ideas come from within (a priori knowledge).
Berkeley, on the other hand, held a position referred to as subjective idealism, which not only claims that ideas come from within but actually denies the existence of an external material world.
2I don't think it's accurate to say that, for Berkeley, ideas "come from within." True, he thinks that ideas depend on spirits for their existence. But that's different from saying that ideas "come from within" if by that you mean that they are products of our will. That's true only of ideas of imagination; ideas of sense, by contrast, do not depend on one's will. See PHK 28 and following. May 14, 2018 at 15:27
"One may view Berkeley’s doctrine on Passive Obedience as a kind of 'Theological Utilitarianism'". From: https://en.wikipedia.org/wiki/George_Berkeley on 10 Sep 2017.
Utilitarian philosophers believe ideas originate from one "Mind" or "God" and therefore ideas should be common property for utilitarian development. Locke in my limited view was less of an utilitarian philosopher and ascribed the origin of ideas more to humans. During the time of Locke, philosophers put much effort in motivations for salaries, due to labor. They did not focus much on the origin of ideas, and remuneration and capital for ideas, because being paid for labor was an important objective. "Theological utilitarianism" was then an even more overpowering paradigm, than today.