2018 Nissan Altima - Sport vs. overdrive

I have a 2018 Altima and it has sport mode and the over drive button so basically over drive is the same as sport mode because they both make the pedal response more assertive

Your Altima has a continuously variable transmission or CVT. It’s programmed to simulate gear ratios, i.e., first, second, etc. “Overdrive” should keep the rpm’s comparatively low, while “Sport” should do the opposite. There ought to be a slight but noticeable difference in modes. If there isn’t, you could have the beginnings of transmission problems. Nissan cvt’s are known for early failure.