I want to understand the contents of PPI (Protein Protein Interaction) Dataset that are available on various websites like one that is available on This LInk.

My understanding is that this data should be in the form of a nx2 vector where each row will tell which proteins are interacting but when I downloaded the dataset like "Scere20170205.txt" from the link I above mentioned I got a huge text file with no detailed information as to what it was representing.

How to understand and most importantly use the PPI dataset that is available around?