There are a few different interpretations of the point of Solos, but the general consensus is that it was meant to be a showcase for young, up-and-coming* actors. It gave them a chance to show off their skills in front of a live audience, and also gave the audience a chance to see them in a different light.
Some people have also said that Solos was meant to be a commentary on the human condition, and how we're all basically alone in the world, despite being surrounded by people. This is a pretty bleak interpretation, but it's not entirely without merit.
*Note: This is not to say that all of the actors in Solos were young or up-and-coming. Some of them were established actors who just happened to be in the show.
