In order to print wirelessly from a printer, you need a printer that has either a print server or WiFi capabilities. Some printers can connect to a network using an Ethernet cable that plugs into a router, but users can set up their own printers, although this is a complicated process that can cost more.
Because wireless printing is a popular concept, many companies such as Epson, Brother and HP manufacture printers that have a wireless networking and hard-wire capability. Some printers allow a connection of an Ethernet cable to a router; others can be wirelessly connected to the network through the computer's network settings.
Another option, albeit more complicated to novice printer users, is connecting an older printer to a Wireless Print Server device. The device is connected through a USB cable, and this allows printers that don't have the capability to network to be used by connecting to a router via the Ethernet cable or WiFi. While this option is viable, there may not be a lot of online support or software for older printers connected to a WPS. Purchasing a wireless printer provides driver and software support and online functionality, and many come with other features such as print software or a built-in scanner.