Image Direct copy/paste in Ubuntu apps

Hello,

I am happily moving from Windows10 to Ubuntu and I have started feeling a little more free. Almost all of my works and projects are running like a charm through my Ubuntu PC and laptop.

I wonder for one more function that I think Ubuntu has, but I can not find it. Eg, at Windows, if you open any image with Paint, and choose the image and COPY it, then you may directly paste it at Word, Gmail etc.

How can I do that on Ubuntu? How can I make a print screen and paste it Directly to gmail new message for example, without having to open the printscreen saved file image?