You will need an internet connection to use Apple TV, but it doesn't have to be wireless. You can connect via an Ethernet cable. If you want to use AirPlay, which allows you to stream content from your iPhone, iPad, iPod Touch or Mac to your Apple TV, you will need a Wi-Fi network. For connecting the Apple TV to your HDTV, this is done with an HDMI cable.
AirPlay allows you to stream whatever is on your iPhone, iPad, iPod Touch or Mac to your HDTV via your Apple TV and a Wi-Fi connection. Whatever you see on your iOS device's screen will be mirrored on the big screen, allowing you to share photos, watch movies, play games, present spreadsheets or whatever else you want to everybody in the room. If you have AirPlay enabled speakers, you can stream your music to them.
Apple's streaming TV service, though not yet officially announced, is expected to launch in September and will likely be viewable on all the same devices that the recently announced HBO Now is compatible with. This means iOS devices including the iPhone, iPad and iPod Touch, as well as the Apple TV. You will likely be able to view it on your Mac desktop and laptop as well. HBO Now will apparently be viewable on a PC, but that remains to be seen for this streaming service.
Although no official announcement has been made yet, Apple is clearly moving forward on putting together content to stream over the web. The company is reportedly negotiating with major networks including ABC, CBS, Fox, Discovery and several others under Viacom. According to The Wall Street Journal, media executives in the know expect the service to launch in September with about 25 channels. The price, they believe, will fall somewhere in the $30 to $40 range.
If and when Apple's streaming TV service launches (currently it is expected in September), the lineup is far from clear. Apple is in talks with Disney (the parent company of ABC), CBS, 21st Century Fox, Viacom and Discovery.