Armour: This is a short section that explains how Armour Class works. There's not much to it, although it does have the table that shows the AC values for each armour type. (The table is needlessly muddied by the inclusion of shields, in a bit of typically Gygaxian over-complication.)
There's a note here that monster AC values don't necessarily correspond with actual armour types. Most monsters have various factors (size, hide, agility, multi-planar existence, etc.) that influence their AC. In short, non-human monsters won't be carrying shields or wearing armour.
It's also noted that shields can only be used against attacks from the front. Later it's said that attacks from behind and from the right flank can ignore shields. This leaves out attacks from the left flank, but I'd be inclined to allow shields against those. I'd also be inclined to allow switching these directions around for left-handed characters.
We learn here that small shields can only defend against one attack per round, a normal shield can defend against two attacks, and a large shield can defend against three. This is something I've never bothered keeping track of, and to be honest it doesn't quite feel realistic. The protective value of shields is massively undervalued in D&D. (I'm willing to be proven wrong here, if any SCA-type folks want to school me on the usefulness of shields.)
Weapon Proficiency: What, you thought you could use every weapon on your class list? Well, not any more, because weapon proficiencies are introduced here for the first time. Basically, every class begins the game being proficient in a number of weapons. There's no bonus for using a weapon you're proficient in, but there is a penalty for using a weapon you're not proficient with. More weapons can be added as you gain levels.
I'm generally in favour of weapon proficiencies, though not always with the way the system is implemented. It's pretty simple in AD&D, and it favours fighters heavily. It's also another way you can customise your character. It works pretty well here.
Weapon Tables: Following the section on proficiencies is a table that shows the damage ranges for each weapon. For the weapons that appeared in OD&D, the damage ranges are much the same. A number of other weapons are introduced here, but rather than getting their own entries they are likened to weapons that already exist on the equipment list. I won't list them all here, because there are quite a lot, and I honestly couldn't tell you what most of them are. I don't even want to Google the Bohemian Earspoon, because I just know that the reality will never live up to the name.
Things get little more complex on the next table, which includes the following information: weapon lengths, space required to wield, speed factor and AC adjustment. None of these are explained yet; I'll deal with them as they come up. Certain weapons are noted here as being capable of dismounting a rider, and others as capable of disarming opponents. Again, there's little detail on how theses are accomplished here. There's a similar table following for missile weapons, with categories for rate of fire, range, and AC adjustment.
Hirelings: This is a short bit about hirelings, as distinct from henchmen. There's not much to write about here, as the section pretty much just says that you can hire people to do stuff. There are some example hirelings given, such as alchemists, armorers, engineers, etc. The only one I've never heard of before is a "linkboy", which sounds dirty, but is actually just another name for a torch-bearer. Actually pretty handy, I don't know why Gary would obfuscate this by using such an archaic term. A character is not limited by Charisma in the number of hirelings he can take on.
Henchmen: Henchmen are a character's devoted followers, and these are most definitely limited by a character's Charisma. Indeed, this is probably the most important thing that Charisma is used for in the rules.
The process of finding a henchman is detailed, with the character having to spend money on visiting inns, posting notices, hiring criers, etc. Non-human characters are generally harder to locate then humans and "semi-humans" (I assume this refers to half-elves and half-orcs).
The PC must pay wages to their henchmen, as well as equip them and provide room and board. They also get a share of treasure, and a share of XP (albeit a smaller one than a PC would gain). I suppose that acting under someone else's instruction lessens the learning experience? Something like that.
The loyalty of henchmen depends on a lot of factors, such as the PC's Charisma, generosity, and how they treat their henchmen in general. As is becoming more and more apparent with the PHB, this is an overview, and the actual numbers are elsewhere )most probably the Dungeon Masters Guide).
(It's a little disappointing that this section doesn't deal at all with pets. There's a bunch of animals ready for purchase on the equipment list, and some guidelines on how to run them would not go astray. There's always some joker who wants to bring his guard dogs into the dungeon.)