opacity and magic wand tool

I learned how to change the opacity of things, i can now make images, backgrounds and texts the correct shade i want. I also learned how to use the magic wand tool.
you change the opacity of things by selecting them on the side column and adjusting it by sliding the button across under the colour palette. 
You use the magic wand tool for a few things, one of them is to remove the white backgrounds from images, you do this by selecting the image on the side panel and clicking the magic wand tool, then you  click the white and click backspace. I think that these are good tools to know because they are quite key and help edition alot. A good editor needs to know how to use these two things to succeed.