WordPress allows you to extend the functionality of your website with plugins.
You can find a plugin for just about anything you can imagine. And if you can't, then you can find someone who can build you one.
There are free plugins and those you must pay for.
Anytime you introduce new code into your website, it increases your risk of getting hacked. It's best to get plugins from only trusted sites or trusted authors. But, sometimes you may not know if you can trust them or not. For this reason, it's also a VERY good idea to have good backups of your website (something your hosting provider should be doing) and a good contact for helping you when things go wrong. No matter how careful you are, you will probably run into a bad or incompatible plugin at some time or another. (You can keep me on speed dial!)
You can find trusted plugins at WordPress.org. These are free plugins. Getting them from WordPress.org does not mean you will never have problems with them, but it means that initially they were inspected to see if they adhered to the guidelines recommended by WordPress.org. I've heard that new revisions added to plugins are not scrutinized as heavily, so an untrustworthy author *could* introduce problems, but it's more unlikely than getting your plugins from elsewhere. If there are problems, they are usually reported more quickly on WordPress.org.
Usually, paid plugins are safe bets too because you have someone to stand behind their code. They will usually offer support for their plugins, but you may have to pay annually to keep getting support. Knowing that someone is supporting the code increases my trust factor a couple of notches. If you don't pay for support, you may not get important security updates to the plugin. Google searches will often give you some insight as to whether the plugin is worth the price.
You can search for free plugins from your WordPress website admin area here: Plugins->Add New
You can either upload plugins that you've either bought or downloaded, or search the WordPress.org plugin repository for free plugins that have been submitted and approved by WordPress.org. Once you've either uploaded or installed via WordPress.org, you will need to 'Activate' your plugin by clicking the 'Activate' button. This will add the new functionality to your site.
You can see a list of the installed plugins on your site by clicking on the 'Plugins' menu option on your Admin sidebar. This will show you which of those installed plugins are activated or not. If you want to disable the plugin for any reason, you can also 'Deactivate' the plugin from this page.
Not all plugins work together well, so don't be surprised if your site quits working correctly after installing a plugin. It may take activating and deactivating several plugins to see which plugins are conflicting with each other. At that point you may have to decide which of the plugins in conflict you really need the most. You may also look for alternative plugins that give the same basic functionality but may do so without conflicting.
You can build your own plugins but that is beyond the scope of this article. We will discuss it in another article.
Plugins are awesome additions to your WordPress site and allow WordPress to do many more things than just be a blog. If you can dream it, there's probably a plugin that can do that!