Although the terms are sometimes used interchangeably, a word’s innermost level of structure is its root (, with a base derived from that, a stem derived from a base, and an inflected word form derived from a stem by addition of an inflectional ending. But for a word with a simple structure, a single morpheme remaining after removing an inflection could be called alternatively a base, a root, or a stem. You distinguish as many of these three levels of structure as you need to, depending on the complexity of the word forms you’re dealing with.
The following articles do a succinct job of explaining the differences and overlaps. I tried to select articles that were not extremely jargon heavy or theoretical. I have some more scholarly articles if you are anyone else is interested. I hope these help: