In my view, these are terminologies used to classify people in terms of their performance ratings. I will attempt to explain the same to you:
Workhorse
These are people/employees who work hard and diligently, often taking extra efforts and initiatives (swift like a horse).
Deadwood
These are people performing at the lowest performance level, often considered poor performers (dead trees and branches).
Stars
These are employees who are the best performers and are often ready to move up to the next level of the hierarchy.
Problem Children
These are people who are better than the deadwood in terms of performance but have yet to go a long way to reach the desired performance level.
In other words, these can be explained in terms of performance ratings as follows:
Stars
Rating 1 - Significantly and consistently exceed requirements.
Workhorse
Rating 2 - Consistently meet expectations.
Problem Children
Rating 3 - Partially meet expectations.
Deadwood
Rating 4 - Do not meet expectations.
I hope, Vijay, I have been able to answer your question to some extent.
Regards,
Prachi