I have been trying to make a comparison between PoW, PoS and Proof of Burn. While I understood the other two, I want to know how exactly Proof Of Burn helps in attaining the consensus. 

One burns coins by sending it to an address where it cannot be spent is what I understood. 
1) But why would one "burn" the coins? Isnt it a loss for the person burning or getting rid of some coins?
2) How is the consensus achieved for the next block in the chain?
3) How is it beneficial in comparison to PoW and PoS?

My apologies, I have read a lot about Proof Of Burn but I am still not able to comprehend.