Yes, the number of teeth does mean something.
But preferably, you need to look at BOTH the number of teeth on the chainring(by the pedals) AND the number of teeth on the sprocket(at the rear).
It's about gear ratios.
Ratio means you're trading one amount of movement at one place for amonther amount of movement at another place.
You can trade a long movement for a short movement, or a short movement for a long movement.
Speed for strength, or strength for speed.
Let's say you've got 44/11 (not very likely, but easy math).
This means the rear wheel turns four times for each turn of the pedals.
(44/11 = 4)
If instead you had 44/14, or 44/15, the rear wheel would only turn (about) three times for each turn of the pedals.
For the same stretch of road, that would require a lot less pedal pressure to push the bike forward at the same speed.
(44/14=3.1 44/15=2.9)
Now you can easily do some basic math and discover that ONE tooth either way doesn't make a huge difference.
But it's there.
Sometimes, even a small change is important.
The smaller a sprocket is, the more important one tooth change becomes.