The bedrooms in my home have two switches for a single light fixture side by side. Just to be clear it is not a two way switch.
The box in the ceiling has a black, red, and white wire but my fixture only has a black and white wire.
What is the red wire for and how am I supposed to use it?
Here is the junction box and the three switches. Left is on off, middle is the dimmer, right is a half hot.
My home was built in the last year so I’m also confused why it was done that way.
Before the days of remote controls, this was the standard for a ceiling fan with a light attached. One switch controls the black wire for the light and the other controls the red wire for the fan (or could be swapped, really doesn't matter).
Depending on how the wiring was done, the white wire is either hot coming down from the ceiling box to the switch or the white is neutral from the switch box to the light.
You can replace the double-switch with a simple single switch if the extra switch bothers you. You can also replace the double-switch with a smart switch, dimmer, timer, etc. but keep in mind that many such switches require neutral, so you may want to check first to see if you have neutral in the box. If the switch box just has the black/red/white cable then you probably don't have neutral. If the switch box has two cables, with the second cable including a black wire going to both switches and a white wire connected to the other white wire then you have neutral (the white wires).
Based on the key updated phrase "built in the last year", it should have neutral in the switch box - i.e., white is neutral not a switch loop hot. As far as "why", if your house was one of many built at the same time, it could be that a ceiling fan was an optional upgrade. It can be cheaper to "wire every house exactly the same" than to save a few $ by using 2-wire cable for some (light only) and 3-wire cable for others (light + fan).
