Jetting forces pressure through water down your line to force built-up debris, smaller roots and blockages out. It also cleans the line so a real picture of the condition of the pipe can be seen.
Two high speed processes can knock those bad boys out! One device used is called the Picote cleaning and the other is called Zip Zip.
Both use a process to remove sewer line blockages in which a solid cable is pushed through the line with a chain attached. When the motor is engaged during high speed drain cleaning, the cable spins with RPM's between 500 & 1500 revolutions per minute. This causes the chains to expand to the size of the pipe. The cable is then pushed through the pipe cutting away roots and debris.