"Unbundled" services means the lawyer doesn't represent you through your whole case. They just work on the parts you ask them to. You handle the rest of your case on your own.
It can cost less than hiring a lawyer for your whole case.
You and your lawyer make a plan to sort out your legal problem. The two of you break down your case into separate tasks and you choose what tasks you want help with and what tasks you'll handle on your own. It lets you work in a way that suits your budget and how comfortable you feel about managing your own case.
Not all lawyers offer unbundled services. The People's Law School Directory of Lawyers is a list of lawyers who do offer them, and what languages they work in. And see Tips about getting legal help for other ways to get help.