Query regarding "Done"

At Sprint Planning the Development Team selects the Product Backlog items that will be worked on and completed during the Sprint.

But just selecting an item is not enough to start working on it. There are some more questions that need to be answered: What shall we start with? Who will work on it? How? When?

It's best if by the end of Sprint Planning all the Development Team members know exactly what they will work on when they come to the office the next morning.

So they need to analyze the selected backlog items, figure out what smaller parts they are composed of, DECOMPOSE them (divide them) into manageable pieces that can be completed in one day or less and assign them to specific developers.

Not everything needs to be decomposed and assigned at Sprint Planning, just enough to get them started. They'll keep decomposing the items further as they work on them during the Sprint.

I'd also like to mention that sometimes breaking down product requirements into backlog items is also referred to as "decomposing." Here's a quote from the PMBOK Guide that deals with agile methods:

"The overall scope of the project will be decomposed into a set of requirements and work to be performed, sometimes referred to as a product backlog."

This is not what the Scrum Guide talks about in the quote you posted. The quote talks about decomposing backlog items into smaller pieces so the Development Team members know what to work on.

Great explanation, Chris. Thanks for clarifying!