What does TTL mean?
I'm new to photography and I see the term TTL all over the place. What does it mean? And how do I use it to make my pictures better?
It means "through the lens" and generally it hooks your flash into the exposure system of the camera since the metering of the scene is through the lens. This allows the camera to exert control over the flash, including power, distance, etc. based on the scene and focal length, if the flash supports that functionality with your camera. Usually true for modern flashes made by the camera manufacturer and some third party options such as Metz.