Tech Text is when poopers use a short or an interesting message usually in form of a gag or a sentenced mixed word. However there has been times when a pooper uses this for a full blown message such as SuperYoshi's CONFESSION series. Sometimes poopers add subliminal messages to their videos that you have to pause at the right moment to see the full message.
The newest feature is Bubble Talkies: a Youtube annotation feature that allows people to post speech bubbles. Immediately poopers edited their videos to create even more bubble talkies. Also annotations in general have replaced this method but some still rely on this for some reason.