ECT:
Puts the transmission in a more "aggressive" mode. The shift points are moved "down" so the transmission is more assertive. It will decrease MPG.
Shift Lock Override:
You must be new to driving. All automatics have this in one form or fashion. Pushing this button will allow you to FORCE the gear shiftier to move without the 1. Brake being applies or 2. The vehicle being on. This is helpful when you need to move the vehicle into Neutral after an accident and the engine is inoperable.
Literally every automatic made in the past 30 years has this.
Hope that helps. Neither are super important in your day to day drive. I never messed with the ECT and I think have used a shift lock override 1 in the past decade. It was an accident and to put it into N for towing.