What Are Filter Hooks?
Like WordPress action hooks, filter hooks are a key/core part of what makes WordPress such a flexible web design platform. These filters allow you to customize different types of content and values with little effort or code involved. So for example, let's say that a theme sets a specific "Read More" text to something like "Continue reading...". What that theme could do is filter that read more text value, providing the web developer an easy solution for customizing that text without having to dig deep into the theme's core code. So let'd take a look at an example of what this theme's filter code might look like:
Note that I included an example of the same value without the filter applied so you can see the difference. On the front-end the results would be the same, with the same "Continue reading..." text displayed, but the filtered example would allow the web developer to easily change that value like this:
With any of these examples above you could quickly and easily edit the theme's own read more text and never have to touch any core code.