Since the Earth rotates all the time, it looks like the stars are moving overhead. So, just like the Sun will rise in the East and set in the West, all the stars in the sky will look like they move from the East to the West. But, stars don't stay in exactly the same place all the time. Both the sun and Regulus do move through space very slowly. A way of measuring this is by looking at the 'declination' of the star.
Declination is a lot like latitude, only for things in space.
It's basically the same as if you figured out the latitude that you'd have to be at for the star to look like it was straight above you. But as time went on, you'd have to move a little bit farther North to keep it straight overhead. So in 2000, it looked like it was just a tiny bit farther North than it did in 1900, as if it were slowly moving from the South to the North.