A text-editor (which replaced an older, more limited editor named TeachText) on the classic MacOS. Launched bloody quickly, but wasn’t terribly interoperable with other OSes, and was limited to only 32K of text. But hey, you could have the computer read the text to you, so I guess it’s not all bad.
I think it’s actually been Carbonized, if you look in /Developer/Applications/Extras.
TeachText lacked a lot of features compared with SimpleText - no styled text, no drag & drop (SimpleText was one of the poster apps for systemwide text drag&drop) and no multiple documents (one window at a time). TeachText’s main purpose was opening ReadMe files in the days of proprietary WP formats before PDF - I don’t know anyone that actually used it as an editor.
I believe that TeachText was written in 68k assembly. SimpleText was written in C.