Paper status "Accept with Shepherd". What does it really mean?

Your paper will be shepherded. The conference organizers will assign a contact person called shepherd to your paper, who guides you through a sequence of revisions (for further information, see the question mentioned by @darijgrinberg, and this question).

The "accept with..." decision signals you that they really want your paper at the workshop, stronger than in the case of a major revision. But similar to a minor revision, there's still a possibility that your paper will be rejected, if you don't work cooperatively with the shepherd.

In my experience as a conference program chair, shepherding is usually applied to borderline papers, where the chairs think the paper has valuable material but flaws too serious for publication in its current form.

Assigning a shepherd for the paper means that your acceptance is conditional on revising to address those flaws. It's still good news, however, in that the conference wouldn't be assigning you a shepherd unless they think that you can overcome the current flaws and produce an acceptable paper. Moreover, it is normally the case that you are invited to communicate back and forth with a shepherd to make sure that your revisions are on target---the conference wants you to succeed in your revision.

What you need to do now is to communicate with the shepherd about your revision plan and make sure that what you want to do matches what they will consider acceptable. If you can find agreement on a set of acceptable revisions and successfully execute them, then your paper should become finally accepted.