An algorithmic penalty is not targeted for you but you're in the blast radius. For example, if Google targets all websites that spam reddit to get traffic, your site may be affected for doing it. These are severe and usually attack hundreds or thousands of sites based on some patterns.
A manual penalty is targeted for your site. For example, if you purchase backlinks from a low-quality seller and the entire network is exposed later, you'll get a penalty for doing black hat. The penalty will show up in your GSC and they mention the type of penalty without revealing exact details. They just say link farms, link exchange, etc. and it's up to you to figure out what went wrong and how to fix it.