What is it for?

It sounds like shift points for the transmission, normal , and a higher power rev point. ECT Electronicly Controled Transmission

Transmission. It changes the shift points for perceived additional power.

That's the ejECT button of course. If you're approaching a condition where it appears the air bag and crumple zones will be insufficient, once it is fully energized, one may eject from the driver's seat. Power and normal are tailored to driver weight.

Or, ECT is electronically controlled transmission. Since the shift points are mapped into the ECU (electronic control unit - car's computer), the button can be used to alter the shift points for greater power. Since the engine produces greater power at higher RPM ranges, the "power" mode delays the shift points, and also will downshift under lighter load. The standard, or "normal" position is recommended for most conditions and is designed to maximize fuel economy. Do try to find an Owner's Manual on eBay. They're relatively inexpensive and will show you other things you need to know. Fuse locations, maintenance recommendations, how to change bulbs, operate the climate controls, etc.