The Hunter is a hybrid class of Druid and Ranger from the Advanced Class Guide. He casts spontaneously, using the six-level spells per day/spells known progression of bards, Inquisitors and Summoners. He learns spells from both classes' lists, taking it at a lower level if it shows up on both lists at different levels. He pretty much takes the animal and nature abilities of both classes and combines them, with a neutral alignment requirement, the weaker BAB of the druid, martial weapon proficiency, and no restriction on armor materials. They also get an actual good animal companion like a druid and actual fighting ability like a ranger.
Unlike some classes in the ACG, as it doesn't combine certain classes' abilities to out-perform either class in a niche but become weak in other niches (for example, the brawler, who will consistently outperform the monk in combat, but has none of the monk's noncombat abilities and much less choice in weapons and armor than the fighter). In fact, probably the class most likely to be under-specialized: can't fight as well as the ranger and can't cast as well as the druid.
Generally not a very popular class due to the aforementioned underspecialization problem and the fact that most people have no interest in teamwork feats.
That said, the class was largely built as a vector for the animal companion, which is pound for pound the best of its kind in the game, so its weaknesses are somewhat mitigated by the power tied up in the critter. It also gets some free buffs from various animal aspects it can attune to.
|The Classes of Pathfinder|
|Core Classes:|| Barbarian - Bard - Cleric - Druid - Fighter - Monk |
Paladin - Ranger - Rogue - Sorcerer - Wizard
| Alchemist - Antipaladin - Cavalier |
Inquisitor - Oracle - Summoner - Witch
| Arcanist - Bloodrager - Brawler - Hunter - Investigator |
Shaman - Skald - Slayer - Swashbuckler - Warpriest
| Kineticist - Medium - Mesmerist |
Occultist - Psychic - Spiritualist
|Ultimate X:||Gunslinger - Magus - Ninja - Samurai - Shifter - Vigilante|