As mentioned in the Filters section, data accessed from URL params (query strings) and form inputs, can be accessed with Articles Anywhere by using the input:... Data Tags.

For example, when passing a category via URL with a custom input parameter, like:

https://www.mysite.com/my-articles?myparam=Animals

You can then filter by that parameter, and display it in the output:

{articles category="input:myparam"}{if is-first}This is a lift of articles from category: [input:myparam]{/if}
• [title]
{/articles}

You can also use this in If Structures, to conditionally output content based on the input value. For example, to show a "HOT!" label for all articles with more than 100 hits, you could add a custom ?min-hits=100 parameter, and then do:

{articles category="My Category"}
[title] {if hits>input:min-hits}HOT!{/if}
{/articles}

Or, for example, you can use this to provide access to registered articles via a URL key (such as ?pass=ABC123):

{articles category="My Special Articles" ignore_state="true"}[title]
{if input:pass="ABC123"}
   [text]
{else}
   This content is password restricted!
{/if}
{/articles}

Note: If you're using Joomla cache (via Global Configuration, not via the System Plugin), you will need to register these additional URL Parameters as "safe", in order to make Joomla create a unique cache for each page. Articles Anywhere allows you to do this in the "Advanced" tab of the plugin settings (for each extra parameter name, you should also specify what type of value it can be).