In the morning, dogs compete by breed. In the afternoon, the top winners from each breed come together to compete in groups. At the end of the day, the top group winners compete for Best In Show. Dog shows are hosted by local dog clubs once or twice a year. In order to attract more exhibitors, local clubs from nearby towns often have their shows in succession at the same location.
People travel longer distances for bigger and better shows.
It is more worth while to travel if you can compete three days in a row at one location. Each day of showing offers different judges so your dog has multiple chances to win. Most of this money goes to the local dog club that hosts the show. It provides for their budget to host their next show and offer educational and club programs throughout the year. Shows cost money to put on so a lot of smaller clubs don't make much profit from their shows.