Relation of the two trees in one root file

Dear ROOT users,
My question is about the two trees (i.e., 2 tree and 1 tree in the image below) in one root file.

image
What is the relation between them?
I have checked the data, they seem to contain the same things.
Then why there are two of them?
Thanks.

regards,
zjw

Thanks. I have looked the User guide. Just want to confirm one thing: Is that the one with the highest cycle number always the right version?

Yes, but typically you can just omit the namecycle and ROOT will pick the right one for you.

Cheers,
Enrico