Proficiency Bonus additions and HD increases

On pages 5 and 6 of the article from UA, you'll find a change in how to apply proficiency bonuses and HD advancement.

Proficiency Bonuses

Once the creature (for example, a wolf) becomes your animal companion its proficiency bonuses are tied to yours. You no longer use the ones on p. 8 of the Monster Manual.

• When you are 3rd level, its bonus matches yours at +2.

• When you are 5th level, it's proficiency bonus matches yours at +3

Wolf AC 13 (natural armor)
HP 11 (2d8 +2)
Speed 40
STR 12(+1) DEX 15(+2) CON 12 (+1) INT 3(−4) WIS 12 (+1) CHA 6 (−2)

The animal companion's proficiency bonus is applied to (this is sometimes significant):

Armor Class
skills
saving throws
attack bonus
damage rolls

The new damage roll for the wolf's bite is 2d4+2+2 at 3rd level; 2d4+2+3 at 5th level; 2d4+2+4 at 9th level, and so on. While early on that + to damage is nice, having +6 damage at 18th level won't make anyone swoon.

It also becomes proficient with all saving throws.

That's a nice feature. Every saving throw the animal companion has to make gets the proficiency bonus (on top of any ability based bonus).

Skills

Your animal companion gains proficiency in two skills of your choice. Whether or not these replace any proficiency or unusual skill from the MM, or adds to them, isn't specified. (These are play test rules, so maybe try it both ways at your table). Pact Tactics and Keen Senses (hearing and smell) would be fine to stay, but that's a DM's call.

For each level you gain after 3rd, your animal companion gains an additional hit die and increases its hit points accordingly.

If you get to 11th level, you'll have added a hit die at each level 4-11. (11d10+con bonus) Your animal companion will add a die at each level up: the wolf would have 10d8(+con bonus) at that point.

ASI based ability increases

Leveling up the animal companion is tied to your Ranger level. Bumping the Dex to 16 at 4th level will help attack and damage a bit. It's up to you where to put the points.

Whenever you gain the Ability Score Improvement class feature, your companion’s abilities also improve. Your companion can increase one ability score of your choice by 2, or it can increase two ability scores of your choice by 1. (Nothing can go over 20)

If you play a straight ranger, you should see ASI increases at 4,8, etc. Do the same for your animal companion. It can't take feats, as you may be able to, but you can boost its stats just as you'd boost your own. If you are multi-classing, you'd see it at Ranger level 4, 8, etc, for the animal companion.

There are three (and a half) versions

• The classic Ranger as given in the PHB.

• The Ranger with No Spells as given in the Unearthed Arcana: Modifying Classes.

  • This version removes the spellcasting progression from the class and gives them a more nature-based theme. This version has included in it Superiority Dice (from the Fighter's Battle Master archetype) and various abilities that mimic spells, but are explicitly nonmagical.

• The Revised Ranger, which is also in the Unearthed Arcana.

  • This version of the class is what a lot of people enjoy. It upgrades the strength of many of the classic Ranger's abilities. Its Favored Enemy and Natural Explorer abilities are so good, it becomes worth it to consider a 1-level dip in this class just for those abilities.

• In the 2019 Class Feature Variants UA the Ranger (in pdf) was given several alternate, or appending features.

  • The core class is still the one in the PHB, but was given optional features to replace certain features (Natural Explorer, Favored Enemy, etc.), append to options (including a Fighting Style which grants druid cantrips), or add to the spellcasting feature (including adding spells to the class list, spellcasting focus, and the ability to replace spells on long rests).

These three (and half) versions of the Ranger are, in essence, different classes which all just happen to share a name. There are, of course, many archetypes/conclaves, but those minor differences do not constitute a totally different release/version of the Ranger.