Streaming a TV show or movie online is in a legal gray area unless done via licensed services such as Netflix and Hulu that charge a small monthly fee to access their catalogs of shows. Unofficial streaming sites dot the Internet landscape, but many of them have poor-quality, malware-laden streams.
Streaming copyrighted material online is quasi-legal. It is illegal when data is downloaded or the stream is played as a public performance without licensing. Many streaming websites such as YouTube operate with pseudo-streaming. Rather than accessing the video in real time, a volatile copy is downloaded to the user's computer. The data remains in RAM as long as the video is open, then is deleted as soon as the window is closed. Software programs and browser plugins are available that enable permanent downloading of streams, but using them to do so constitutes copyright infringement.
Watching a show online in private without permanently downloading the data is unlikely to draw the ire of a copyright holder. Uploading streams, however, is highly illegal and carries imprisonment and fines as penalties should the uploader ignore cease-and-desist letters. Similarly, playing a stream for a large group of people is considered a public performance that generally falls outside fair use copyright laws.