What is Optimistic Latch-Free Index Traversal in SAP HANA Architecture?

I heard a buzzword "Optimistic Latch-Free Index Traversal" in one blog post on Introduction to SAP HANA by Dr. Vishal Sikka. I googled about it in context of SAP HANA Architecture but didn't find anything concrete. Could someone please explain this whole concept thoroughly, in context of SAP HANA?