DnD 5e - Armor and Shields
Most adventurers depend on manufactured armor to protect them from attacks. Armor comes in several varieties, each of which is described in detail on pages 144 and 145 of the Player's Handbook. This section will cover the rules around armor, but I will not reproduce the table containing individual armor stats. Instead, check page 145 of the Player's Handbook. It's helpful to know where to find the table so that you can reference it when you're shopping for armor.
The official rules provide stats for just 12 types of armor. These suits of armor provide an approximation of the countless, diverse types of armoor which appear in real-world history. While these 12 suits may not perfectly match any historical artifact, they provide enough variation that you can typically match real-world armor to one of the types listed in the Player's Handbook.
Any character is capable of donning a suit of armor or strap on a shield, but proficiency is still important. If you are wearing a suit of armor in which you are not proficient, you suffer Disadvantage on Strength-based and Dexterity-based attack rolls, Strength checks, Dexterity checks, Strength saving throws, and Dexterity saving throws. In addition, you are wholly unable to cast spells.
It's rare for a character to intentionally wear armor in which they are not proficient. The penalties are simply too steep to justify it except in unusual circumstances like wearing a disguise.
Manufactured armor provides a new formula by which to determine your armor class. This formula for each suit of armor is detailed on page 145 of the Player's Handbook in the "Armor Class (AC)" column of the Armor table.
For more on Armor Class, see Attack and Defense, earlier in this guide.
Certain types of armor are bulky, unwieldy, or simply noisy to move around in. These types or armor give the wearer Disadvantage on Dexterity (Stealth) checks. Armor which imposes Disadavantage on Dexterity (Stealth) checks is indicated in the "Stealth" column of the Armor table on page 145 of the Player's Handbook.
Armor comes in three varieties, plus shields: light armor, medium armor, and heavy armor. Armor is worn on the body like an outfit of clothing, and covers the body at least partially.
With some rare exceptions, you want to wear the most expensive type of armor within whichever category makes sense for your character, so adventurers who can afford it are most commonly found in studded leather, half plate, of full plate armor.
I'll cover each category of armor briefly, but for descriptions of individual types of armor, see pages 144 and 145 of the Player's Handbook.
Light armor is made from supple and often thin materials, and is designed to complement the wearer's Dexterity, representing their own ability to avoid attacks. Creatures wearing light armor add their Dexterity modifier to the base AC provided by the armor, so light armor is recommended for characters with Dexterity modifiers of +3 or greater. Light armor includes padded armor, leather armor, and studded leather armor.
Medium armor offers more protection that light armor, but it's also more restrictive. While wearing medium armor, you add your Dexterity bonus, up to a maximum of +2, to the base AC provided by the armor. Medium armor is best for characters with a Dexterity bonus of +2, or for characters with a lower Dexterity bonus who aren't proficient with heavy armor. Medium armor includes hide armor, chain short, scale mail, breastplate, and half plate.
Heavy armor offers the best protection, totally disregarding the character's Dexterity in favor of relying solely on the armor's ability to deflect attacks. Heavy armor provides a static number as your AC, and you do not add your Dexterity modifier to this value, even if it's negative. For this reason, heavy armor is a great option for characters with Dexterity modifiers of +1 or less. heavy armor includes ring mail, chain mail, splint armor, and plate armor.
Shields provide an additional +2 bonus to your AC on top of whatever Armor Class calculation you're using. Manufactured armor, natural armor, and even the Barbarian's Unarmored Defense class feature all work with shields. However, using a shield means that you can't use a two-handed weapon, and you can't hold other objects in that hand like other weapons, wands, potions, etc. 5th edition Dungeons and Dragons only presents one variety of shield, and it's the sort of shield which is heavy enough that the user must hold a handle on the shield for it to be effective, so you can't hold other objects like torches while also holding a shield.
Getting Into and Out of Armor
Putting armor on is called "donning", and removing it is called "doffing". You rarely need to worry about how long it takes to don or doff your armor, but it takes an Action to don or doff a shield (which sometimes you'll need to do during combat). If you need to know how long it takes to don or doff armor, check the "Donning and Doffing Armor" table on page 146 of the Player's Handbook.