Lion's Share - example and meaning

He did the lion's share of the work, so he deserves the majority of the credit.

So, what does "lion's share" mean?

The lion's share refers to the largest or major part of something. 

It comes from a fable where a lion claims the majority of the spoils for himself.

So, in the example, he did the majority of the work, and that's why he deserves the largest part of the credit.