Prions-What are they ? Protein Misfolding Mechanism

A prion is an infectious agent composed entirely of protein material, called PrP (short for prion protein), that can fold in multiple, structurally distinct ways, at least one of which is transmissible to other prion proteins, leading to disease that is similar to viral infection. They are suspected to be the cause of transmissible spongiform encephalopathies (TSEs) among other diseases.

In This video the following things have been discussed:
What are Prions ?
How they are made ?
Why normal protein becomes Prion ?