A WiFi network is set by a router, the router creates a wireless access point. A router is a network device and as every network device it can support up to 255 connected devices. You can connect from 1 to 4 wired devices to the router and the rest are working with wireless.
Theoretically connecting 255 computers to a single WiFi access point is possible, but talking about performance is not recommended at all. The router will not have that performance to work with all these connected computers at the same time. The network will be very poor, to improve it better install more access points, so router will manage easier the connection and work.
For your personal network at home, sure you can connect some dozens of computers, if you know that you’ll have a big number of devices and computers on WiFi try to get a more expensive router as it’s faster and more productive.