The Clash of Clans shop allows you to buy all sorts of things for your clan, including buildings, resources, defenses and decorations. There is a total of six options once you reach the Shop, and you can get a breakdown of these by looking below:
Select the Treasure category to be able to buy yourself resources that you would otherwise have to wait an age to build up. These include Gems, Gold, Elixir and Dark Elixir. You will be using real money to buy them, unfortunately there's no marketplace-style trading Coins for Elixir or anything like that. You pay using Gems (a.k.a. real money) and get resources back in return.
Don't get confused between this section and treasure - you can't actually purchase any resources from this area. Instead, it is for the actual resource producing buildings. This list also includes Builders' huts.
These are by no means an essential part of Clash of Clans, but are fun distractions that can help to make your village more unique. The one useful thing about them is that enemies cannot be deployed on them, so placing them in strategic locations is a good plan.
It should be fairly obvious that this is where you find all your offensive items. These, at a glance, are Army Camps, Barracks, Laboratory, Spell Factory, Barbarian King, and Archer Queen. If you concentrate on upgrading all of these structures, you will end up with a strong offensive capability.
Essentially the opposite of Army, this is arguably the most important section of all. While attacking takes skill, planning and a strong infrastructure to support your troops, the difference between a poorly constructed base in terms of its defensibility and one which has had little thought put into it, is massive. It is possible to play Clash of Clans almost entirely as a defensively-minded player, although getting enough resources to fund your defensive structures is hard. Building placement is vital, as is upgrading your defenses. Things to bear in mind about this section, just briefly, are that you should be trying to safeguard your resources and trophies. If you lose your Army Camp also, you will lose all the troops within it. The Defensive buildings on offer include the Cannon, Archer Tower, Walls, Mortar, Bombs, Air Defense, Spring Traps, Wizard Towers, Gian Bombs, Hidden Tesla, and X-Bow.
The final section is Shield, where you can purchase a Shield to safeguard your clan from attack for a set period of time. This can be one day, two days, or an entire week. After using a Shield, you have to wait a certain amount of time before you can use it again. If you attack in multiplayer while the Shield is active, it will be deactivated.
You receive a Shield automatically when you are damaged to a certain degree - you receive a free, 12 hour Shield when you are damaged to 40% and a 16 hour one when you are 90% damaged.