difference between ibid and ibid-with-locator

CSL Development
1

Hello,
What exactly is the difference between “ibid” and “ibid-with-locator” in
the csl schema?

Author, /Title/, Bucharest: Humanitas, 2005. (this is “first”)
Ibid. (this is “ibid”)
Ibid., pp. 50-55 (IS THIS “ibid-with-locator”)?

Thank you very much,
Nicolae