Hi,
I have written many articles about ListNerds which document my journey and are worth a read. But in a nutshell, you promote your blogpost/business and people view the mail and if you get enough upvotes, you can earn some crypto, get extra views/upvotes on your blog.
Here is a good starting point of how it looks like compared to traditional marketing:
https://ecency.com/hive-119826/@mypathtofire/listnerds-changing-online-marketing-with
The free membership is a no brainer and is a good easy fun way to get started.