Inspiring, exciting, historical (watch the ones of Steve Jobs, Dan Gilbert or Amy Cuddy) and motivational. From all of them you can learn. TED confirm three things. One: sense of humour catches the attention. Two: it's not about the quantity, but the quality. And three: a good idea is a powerful virus.
Technology, entertainment, design. These are the initials of TED talks, an initiative born in California in 1984 so as to give voice to ideas that would be worth sharing them. TEDs last, more or less, a quarter of an hour. If the it's a good idea there's no more time needed. A project, a theory, an hipothesis or an anecdote + an audience that listens + 15 minutes so as to enkindle the enthusiasm in the grandstand. If you try it, you get hooked.