The new MacBook Pro comes with two or four external ports, depending on the model you pick. And the new MacBook Air has a pair of ports. But those ports are only of one type: Thunderbolt 3, which is compatible with USB-C.
But you probably have devices that use USB-A, Thunderbolt 1, Thunderbolt 2, DisplayPort, HDMI, or something else. How do you connect these devices? With an adapter.
If you’re planning to buy a new MacBook Pro or MacBook Air, make sure you set aside a considerable amount of cash for the adapters you need. Apple doesn’t include any in the box, except for a power adapter.
Your best bet is to get a combination dock, like the Satechi Slim Aluminum Type-C Multi-Port Adapter ($60 on Amazon). It connects via USB-C, and includes a USB-C pass-through port, two USB 3.0 ports, and an HDMI port with 4K (30Hz) support. With this, you don’t have to carry around multiple adapters.