Difference between "Photos" and "Pictures"

You have a choice.

I want a folder that contains ALL of the photos in my computer

You will only get that if you put them there.

You can use the Photos application which is a media manager that manages all your photographs, with useful editing tools and allows to to edit non-destructively, and share the images to any app you want or for whatever need you may have. You access that by clicking on the Photos icon on the Dock.

If you prefer there are other applications for this task, most more powerful than Photos, but for those you pay.

Or

Stick all your photographs in a folder. You can use the Pictures Folder or any other folder you choose. You can create a folder for the purpose. It's entirely up to you.

The first option requires a small learning curve but it is more flexible and makes managing your photographs easier.

The second option is simple to set up. That is its singular advantage. It's just lots of files in a folder.

Now you have to choose. One or the other.

Are you asking about the difference between the Pictures folder and the Photos Library?

• When you are using the Photos.app to organize your photos, all photos you import to Photos will be copied by Photos into to database called Photos Library.photoslibrary. This is a closed package with internal database files and working copies of your Photos. We need to run Photos to access the photos there and to retrieve them for us.
• The Pictures folder is a predefined folder created by the system, where many applications are looking for our photos by default. You can use this folder to store your photos or ignore it. It is not compulsory to store our photos there but other convenient to have just one place where to look for photos.

Feel free to ask as many questions as you like or need. There is no upper limit.