This site: https://www.space.com/mars-at-opposition-2020-starry-night-software is typical - it says that Mars is closest to the Earth Oct 6, and at Opposition Oct 13.
Opposition is when the planet lines up exactly 180 degrees away from the sun. You would think that this would be the closest as well, but I can see with elliptical orbits this may not be so.
But that site also says “Next Tuesday, Oct. 13, Mars will officially reach opposition, and maximum brightness in the sky.” which I find weird since it is further away than it was the week before. Unless it has something to do with the sunlit disc we are seeing.
Your insights would be appreciated!