bompani calor choice free standing oven?

I have been given one of the above cookers its gas the only way you can ignite it is by plugging socket it into electic plug or ignition wont commence. At the bottom of the oven inside at the front is a small metal button (hollow inside) it goes up and down when pushed
1....what is this for??
2.... i know bompani do caravan cookers if this is one can it be used in a home ???
many thanks