A self launching glider is just a glider with an engine. Some (such as we have available) look like a small aeroplane with very long wings. It is heavier than an equivalent two seat training pure glider but has a similar gliding performance when the engine is switched off.
It requires only the pilot (and if desired a trainee or passenger) to operate it, contrasted with winch launching which requires a crew of four or five for safe operations. Being heavier, it takes a stronger thermal or "lift" to enable it to climb when the engine is off. The big advantage is that you can use the engine to go wherever you want to and (within reason) as high as you want to, then switch the engine off to glide.
Some other motor gliders which are more sophisticated have a retractable engine and/or propeller so that when the engine is shut down it has the same profile as a glider without an engine. These are very expensive machines!