On the use of numpy.random.RandomState

What is the difference in

a = numpy.random.RandomState(1)
b = a.rand()

compared to

b = numpy.random.rand()

I'm not really sure if this has to do with seeding, and I'm new to the concept of seeding. If this is a case of seeding could somebody explain how the RandomState method does that, and maybe any tips on when it's useful to seed. Thank you.