It's a parenting programme aimed at teaching parents a way to interact with their children by receiving immediate feedback on how they are interacting.
A key aspect of being a parent is to set the behaviours of our children by the way we interact with them. Enforcing good behaviour by being a positive role model. One way is for a parent to display good behaviours, e.g. tidying up after themselves or how we talk to immediate members of the family (as an example, if you back-talk or are disparaging to your partner, your child will start to mimic it).
This particular type of parenting program focuses on your immediate interactions with your child and provides feedback from an observer. As an example, say you're sitting at a table playing playdoh with your kid. He attempts to eat the playdoh, you smack his hand away from his mouth and call him an idiot for trying to eat it. You may do this subconsciously, not noticing what you are doing, mostly from the concern that he will harm himself. The observer will point out a different way of performing that interaction.
Done well it's a good part of the mix of skills that are needed to be a decent parent, but you must realise it's not the be all and end all of learning how to be a good parent.