NEWBIE QUERY

This is a good starter course:

https://www.youtube.com/watch?v=IyR_uYsRdPs

You can learn right in Photoshop itself. Many of the most important skills are covered in the tutorials in the Learn section of the Home screen that you see when you start Photoshop. And, some of those are hands-on tutorials, meaning you get to follow the steps yourself using lesson files that Photoshop automatically downloads for you.

I would recommand you to start with the "learn" section at  Adobe.com
there is a bunch of short videos and easy tutorials

that will get you started with photoshop.

The Piximperfect's " Photoshop for Beginners" Playlist on Youtube is a great starting point too.
The "Photoshop Training Channel" offers a lot of great tutorials well explained by Jesus Ramirez.

I'd recommend learning the basics of how Layers, Channels and Paths work. Most of the fundamentals in Photoshop revolve around those concepts and build upon them. There are lots of how-to videos on YouTube and other web pages explaining them in more detail.