WordPress has a set of core files that will never be changed by a developer. Hacking the core files is the ultimate sin. The main reason for this losing your changes when there is a wordpress update. Instead what you would like to do is add on hooks. So for instance if you wanted a site that has e commerce functionality – ie if you wanted to sell stuff online – you would just add a hook to the core files of wordpress. A hook can be known as a plugin too – although that can be disputed. In essence the idea is the same. referring to e commerce functionality, you can download and install a plugin called woocommerce. You don’t need any previous programming experience too!
Anyway back to the task at hand; hooks are functions that can be added to the core files – just in case you missed it.
There are two types of hooks, an action hook and a filter hook. The action hook triggers when a particular page is loaded. For instance, if you wanted to have a pop up window each time a page is loaded, this is an action. Actions add or remove functions.
The filter hook is designed to change, generally, existing content. The best way is by example. Lets say you have code that drives your comments section on your blog – here you could have something like a profanity filter. you have a filter that checks the comment to make sure no profanity is included.