Lat engagement suddenly clicking?

42m, started swimming about 4-5 months ago currently doing 1:55/100m average over 1500m 6 times a week. I've watched the various videos on technique but haven't had any coaching or training (beyond learn to swim age 8 or whatever).

Today felt a little different for some sudden reason. At the end of my reach just at the last moment before beginning the catch I felt like I could do a very slight extra reach and that allowed my back, just outside and below my shoulder blades to tighten. Then the whole of the catch and pull felt like it was pulling through with that tightened muscle with way less effort on the actual arms.

Is THAT what they mean by lat engagement? Am I meant to be doing that all the time? It kind of just suddenly clicked today.

It didn't necessarily lead to any increased speed but it probably did feel easier. I had been doing a 2 stroke breath in order to keep enough oxygen over the distance but using the back like that meant I could slow to a 4 stroke breath to concentrate on form without suffocating (yes I know, work on 3 stroke).

Back sure is sore now!