Those terms were introduced on a web site that offers free provider web sites.  As the free sites have become more popular recently, some of the terms have gotten more exposure and use.

Here is a partial list of those definitions (the ones that do not appear in the TER 'Definitions, Acronyms, Abbreviations, and Terms' post - see link below):

A-Level (5 star escort, includes anal)
CID (Come In Deep)
COB (Come On Body)
COF (Come On Face)
Completion (Oral to completion)
Duo (Sex with two escorts; Threesome with the client)
Extraball (Have sex many times)
LT (Long Time; Usually overnight)
O-Level (Oral sex)
OWO (Oral without a condom)

Many of these terms are British in origin.  YMMV when applied to escorts using them in the U.S.A.