YouTube is the preeminent video sharing website. Users create and upload their videos to be seen by a worldwide audience. According to the Internet tracking service Alexa, YouTube is the #3 most visited website in the world (after Google and Facebook respectively).
Founded by three former PayPal employees in 2005, YouTube has had a profound impact in the way the world interacts. In November Google purchased YouTube for a reported $1.65 billion.
Before YouTube, there was no easy way to share videos on the Internet. Even sharing pictures wasn't easy, with services like Picasa and flickr still in their infancy. Practically overnight, the ability to share videos with friends became as common as email.
YouTube is best known for it's funny "viral" videos that are shared and shared and shared until the number of views is in the tens of millions. One of the most popular videos "Charlie Bit My Finger" that shows an infant biting the finger of his slightly older brother, now has a staggering 283 million views, significantly more than the population of most countries.
What is less apparent is that YouTube is actually the world's most popular music site, with music videos and videos that just feature music consistently among the most viewed videos on the site.
The site that's the most similar to YouTube is Vimeo, but in reality nothing comes close. On the pay side iTunes and Amazon Video on Demandare the most similar.
Many new Blu-ray players and TVs have access to YouTube, though searching tends to be difficult, as they lack a real keyboard.
Though there are some videos available in 720p, overall picture quality is very poor. Worse for the non-HD videos. User uploaded videos tend to be nearly unwatchable on large screen TVs.