An arcade cabinet (“cab” for short) is a machine, usually somewhat boxy, that houses the computer hardware, monitor, game software, coin slots, joysticks, buttons, and so forth.
You can buy one if you have the money, but usually they sit in an arcade, being owned by an operator or being maintained by an operator and owned by a game center, and you pay per play.
If you would like to operate your own cabinets, you must understand certain ramifications: for example, these things take power (which costs money), and if you would like other people to pay to play, you will probably have to comply with lots of laws (which can be a royal pain), be willing to pay for maintenance that isn’t your fault in the least (which costs money), be aware that you may be held liable for incidents occurring under your watch (which costs money), and so on.
Needless to say, you should only be doing this for the love of the game. There isn’t a whole lot of money to be made in it these days.