Major headache, grounds for divorce, plausible excuse for murder, etc.
But actually the answer is much more complicated. The quick answer is a deployment unit that usually includes content such as .aspx application pages, list schemes, settings expressed in CAML (potentially huge XML files without a lot of documentation).
JD's suggestion for Ted Pattisonโs book is good, but I suggest putting together a few books because you usually find something in one that you donโt find in the other, and this will help you see what is required by agreement and which is only a specific preference the author.
You really need to comb a lot of different sources and plan to spend considerable time on SharePoint before you become comfortable with these concepts.
Josh
source share