What is the meaning of double percentage signs with square brackets?

Question

I am currently working inside a Marketing Cloud Landing Page. The page has code inside an HTML block. Some of the code is within a script tag like this

<script type="text/javascript">CODE</script>

Which I can understand, as being javascript code.

But other code is enclosed with double percentage signs and square brackets like this.

%%[CODE]%%

Which I don't quite understand and sadly couldn't find anything about online.

What does it mean if code is within these characters? What programming language is this?

Answer 1

%%[<code here>]%% means that the code contained is AMPscript. A proprietary, embeddable language (php would be another example of an embeddable language) used on Salesforce's Marketing Cloud.

There are a collection of modules/trails dedicated to AMPscript on trailhead that should help you get started.