Why is there one fewer solar day per year than there are sidereal days? solar day = time between solar noons
sidereal day = period of Earth's spin
Wikipedia says "relative to the stars, the Sun appears to move around Earth once per year. Therefore, there is one fewer solar day per year than there are sidereal days."
Shouldn't it be relative to the Earth instead of the relative to the stars? I'm having trouble following this argument. Can someone please explain it in more detail?
 A: On the specific wording in question
Relative to the Earth would normally mean the Earth is fixed in place. So days relative to the Earth doesn't exactly make sense.
Better, quoting the exact section linked:

The stars are so far away that Earth's movement along its orbit makes nearly no difference to their apparent direction

If it helps, it's basically the same as saying "relative to the universe".
Explanation
(similar explanation to the Wikipedia article)
In the frame of reference of a solar day, the Sun and Earth are always in a fixed place - say, the Sun directly above the Earth.
On the other hand, in the frame of reference of the stars (universe), the Earth orbits the Sun once per year. Equivalently, the Sun may seem to orbit the Earth once per year.
If this isn't intuitive, pretend there's someone walking around you in a circle, and you keep in eye contact for a whole revolution. They're moving around you, so you're definitely turning a full revolution - and they're always looking in the opposite direction (= at you) - so they must have also turned a full revolution - and since they're always facing you, you must have appeared to made one orbit around them from their perspective.
So no matter how many days are in a year, since the Sun appears to make a full revolution around the Earth, it essentially "catches up" with one spin of the Earth, which is why there is one fewer solar day than sidereal days in a year.
A: 
Shouldn't it be relative to the Earth instead of the relative to the stars?

We need some reference background to plot the "movement" of the Sun. If we could see the stars during the day, and we were to go to a fixed point on the equator and mark the location of the Sun each day at noon on a star chart, this point would move in a circle through the stars once per year. The Sun rotates around the Earth more slowly than the stars do, so the number of solar rotations is one fewer than the number of sidereal rotations.
Imagine walking counterclockwise around a circular track, facing North the whole time. Suppose there's a light in the middle of the track. If you start out in the Eastern part of the track, the light will start out on your left. Once you get to the Northern part of the track, the light will be at your back. When you get to the Western part, it will be on your right. At the Southern part, it will be in front of you. So the light will appear to rotate around you counterclockwise.
So if the Earth didn't rotate at all, the Sun would appear to rise and set once over the course of the year. This one circuit due to the revolution around the Sun cancels out one of the 366 circuits due to the rotation of the Earth, leaving only 365 solar cycles.
A: Work it out for the limiting case of a planet rotation-locked to its sun (as the moon is to the Earth). There is one sidereal day per orbit, but the solar day (or night, to see the stars!) lasts forever. Now imagine a planet rotating once on its axis for each orbit around its sun. Draw the situation at four quadrants. If you need to, then draw two rotations per orbit, drawing the  situation at every sixty degrees of orbit. You'll soon understand (in a true-understanding way, that can't be arrived at with mere words).
If this sounds condescending, that's not my intent. It's what Feynman always recommended, that an intuitive understanding of a concrete model is important, even when (unlike this one) the concrete model is only an approximation.
A: From this youtube video comes this frame:

Relative to distant stars, Earth takes 23 hours and 56 minutes to spin once around its axis. During that time, it also orbited a little bit on its way around the Sun. Thus, to catch up, it has to spin a few extra minutes such that it's again noon at a given location. That's the 24 hours between noon and noon.
I find that Wikipedia sentence confusing too, but if you read the paragraph leading to it, I think it is rather clear how this works.
A: Taking the perspective of a person who believes they are the center of the Universe, the stars circle the The sky once per day. The sun kind of does too. But since (gasp) Earth actually orbits the sun, each year the sun makes one fewer “transit” across our sky compared to all the other stars.
Is that correct?
A: An easy way to picture it is imagining the case if the Earth was tidally locked.  In a year, it would rotate once from a galactic perspective, but the Sun would remain fixed in the sky...0 solar days, but 1 sidereal day.
A: Take an example of a clock having minute and hour hand to understand why there is a day missing in a sidereal year to number of sidereal days in a sidereal year.
In a day of 12 hours, hour and minute hand align at zero hour and again align after 12 hours respective to same position in background. Now the time taken by minute hand is 1/12 days per rotation and by hour hand is 1 day per rotation, therefore the difference of time is,
1 - 1/12 = 11/12 days per rotation
This is relative time measure by an hour hand of a minute hand. So in duration of 12 hours, total time taken by a minute hand seeing from hour hand is,
11/12*12 = 11 hours per rotation.
There is one hour missing from a complete rotation of an hour hand which is of 12 hours. So an hour hand counts a day of 11 rotations of minute hand which is 11 hours as 1 rotation of a minute hand to the fixed position of the background is 1 hour.
So when earth or ecliptic completes there 360 cycles, sun or earth complete 1 cycles. From point of view of year, there is one day or cycle less. Here rises one question that, is a day fundamental unit or a year. Answer is a year, which is divided into parts as day because we are observing from year's point of view. It also questions heliocentric view, from it only earth is moving for both day and year, so there should no two different perspective, but it are.
