Broadcasting using YouTube WebCam
YouTube's WebCam feature lets you host your webinar directly from your browser without having to download any software onto your computer. It connects to your computer's webcam and microphone and can broadcast with very little delay.
This is a great way to get started and lets you setup a webinar very easily but WebCam cannot be used to share your computer's screen. If you need to share your screen you'll need to use an encoder as described below.