Firstly all snakes are not poisonous. All of the Serpents are Venomous except some; now the snake's used in shows like "Khatron ke Khiladi" are not venomous at all. Most of the snakes used in these shows are belonged to boa & pythonidae families of snakes.
Difference b/w venomous and poisonous?
Now in both condition the creature is toxic.
But the venomous one's are those which need to deliver or inject the venom directly into the body of other organisms, for this they have specialized instrument such fangs in snakes while in case of poisonous animals they are only be toxic if they are eaten or being touched.