The nonchalant text u send immediately before you send an important text to a person. The pre-text insures that you will know whether or not the person will reply so that you are not left with textpectation after sending the important text it insures that your important query will not be textnored. Sort of like signing for a UPS package so they know that you got it.
Dude I wanna ask Bertha on a date but if she doesnt wanna go she'll just textnore me and say that she never got it. I'll send her a pre-text saying "What's up" then if she doesn't respond to my text asking her on a date, I'll know she's super shady.