Explain intermolecular hydrogen bonding with reference to ortho nitrophenol

Look at the first and third pictures. The first is straight o-nitrophenol while the third one shows the H bonding.

https://www.google.com/search?q=orthonitrophenol;&tbm=isch&tbo=u&source=univ&sa=X&ved=0CDQQsARqFQoTCIHhi-PomccCFYKPDQodCewOqQ&biw=1011&bih=601