There are 3 stars in the Alpha Centauri system: 2 large stars orbting around each other (A & B) and a distant Proxima Centauri (C) orbiting around both.
Right now it just happens that Proxima Centauri is in the right place in its orbit that it is the closest star in the system to us.
But when will that change and the pair of Alpha Centauri A and B will become the closest?