A partition is a fraction of the whole hard drive. Each partition gets recognized by the computer as separate volumes or connected drives. Setting up partitions can be helpful in many cases such as setting up BootCamp were you need to run Windows separately. Another example is when you want to split up data like most computers now have a recovery partition which helps to fix problems on the main user partition.
During Apple’s World Wide Developers Conference (WWDC) Apple unveiled new computers including the iMac and MacBook. All computers except the MacBook Air, Mac Mini, and Mac Pro included the addition of Intel’s new Kaby Lake processors. They also updated the Thunderbolt port on the iMac changing the 2 Thunderbolt 2 ports to 2 Thunderbolt 3 ports.