The word "technicalities" has no precise (no specific) reference to any one thing in the law. Indeed it is used mainly by laymen who are disgruntled by how the law actually works. People say "He got off on a technicality," which often means that a defendant won
but they do not like it. To some people, a defendant "got off / got away with it on a technicality" if the defendant won, even if there was a full trial on the merits.
In other words, people use the term almost indiscriminately. However, I'd say that the general thrust of the term is that it refers to someone who is perceived to have won despite being guilty in fact.
"Skating" refers to getting out/skating out/slipping out of the problem.
Someone else will likely find more precise wording for you, but the foregoing gives you the gist.
