Photoshop is the industry standard and it takes a while to learn but it's a skill worth knowing. I like slightly older versions that will still install on a Mac or PC and not require web login, and monthly subscription fees!

Just like for video editing, it's very hard to beat Premier, so I have stopped trying. It is an amazing professional video editor..

AVID makes more professional software but the price is astronomical (for video). But often I just want to cut up a video and create a new start and end point (crop the video down to shorter time/ size). I also don't want to re-encode the video (because it will add distortion) so I use Boilsoft Video Splitter and Joiner for quick video edits with no re-encoding.

https://www.quora.com/What-is-the-difference-between-Adobe-Photoshop-and-GIMP

A lot of people can do a lot with Paint. I use paint for very simple things; photo resize and crop. But not for much else. I only use these tools occasionally; so sometimes I work with a demo copy of photoshop and uninstall it later. Each new version will allow you to install a 30 day demo ;-)

All these tools are so common that there are many tutorials for how to use them. GIMP included; but it's not my favorite.