How many versions of the Ranger class are there in 5e, and what are the differences between them?

I was considering building a Ranger, and consulted my local game shop DM on the matter. He suggested using one of the revised versions of the ranger class, due to the ranger in the PHB being somewhat underpowered as compared to later revisions of the class.

I was also doing some reading, and found a couple of references to a “revised ranger” here and here.

How many different versions of the ranger class are there in 5e, and what are the differences between them?

I’m looking for answers that reference official WotC sources, including UA if it’s applicable.

I’m not asking “How many different ways, subclasses, feats, etc. are there for designing rangers?” Rather, I’m confused since there appear to be multiple releases of the ranger class itself, yet the only version I am familiar with is the version in the PHB.