A TEDx Talk is a showcase for speakers presenting great, well-formed ideas in under 18 minutes.

Why under 18 minutes?
This short talk model works, since it only demands the audience's attention for a short period of time, decreasing the chance of minds wandering or daydreaming about lunch. In fact, some of our greatest TED Talks have been as short as 5 minutes long!

What is a great, well-formed idea?
It can actually be one of two things:

Something that’s new and surprising; an idea or invention that your audience has never heard about.
A great basic idea (that your audience has maybe already heard) with a compelling new argument behind it that challenges beliefs and perspectives.
In other words, an idea isn’t just a story or a list of facts. A good idea takes certain evidence or observations and draws a larger conclusion.