The pigeon update is a new Google algorithm update that affects only local results. There isn't much information about it yet so we don't know what criteria it used to penalise and elevate websites. It was named the 'pigeon' update by Search Engine Land. Pigeon is not the official name of the update.

Pigeon: Search Engine Land's Name For The New Google Local Search Update

that post has no evidence, Just a random claim.

Its the algorithm that is being introduced by Google that would affect the local search and will eventually works out in a traditional manner. I don't think that its officially declared. Even I came to know about the same from some article.

Shouldn't affect your normal sites

It's for local sites, making the SERPs more like regular SERPs than the old 7 pack. But no one really knows how it's going to affect things yet. Some people saw dramatic rankings movements for local terms, but they seem to have stabilized.