ServSelect is a range of KVM (Keyboard / Video / Mouse) switches for computer use. Essentially they allow you to connect a large number of computers through one console - very useful in test environments, or for servers, especially if they are usually access by remote control and true local logins aren't needed very often.
Early KVM boxes were simply mechanical devices that had a switch on the front to connect 2-4 machines to a single console. However, with modern machines (and especially those with mice) these don't work very well... Windows often doesn't recognise a mouse once it's been disconnected. The newer electronic ones emulate a keyboard and mouse internally, so every machine connected to them permanently thinks it's connected to a keyboard and mouse regardless of which one is actually "online" to the real console.
Some KVM switches have buttons on the front panel to select the machine to display... the higher end ones also have advanced interactive menus, usually brought up by pressing some hotkey (PrintScreen or Control twice are quite common). This allows you to define names for the machines etc. They also do clever tricks like broadcasting keypresses to all machines, and automatically scanning between the ports.
Finally, you can daisy chain KVM switches together, and if they're the same make and model, they can often control each other - so you see a single list of all the machines, and can select the one you want to control. The appropriate "chain" of KVM ports is then selected in the background.
(Of course, the problem with these is that companies like mine end up with a huge surplus of keyboards, as most machines come with these even though we don't use them!)