What is the best way to put a bunch of photos on one page?

Question

Web development

Hello.
I often saw sites where there are 20-100 small sized photos on a page and this page loaded quickly.
And when you click on them, they could increase.
They were originally all the size of the screen and just reduced them to the size of the menu?
Or are they all small initially and when you click on them, they are already loaded from the server in full size?

Answer 1

For previews, designers usually give a minified version of the image.
And when you click, there is already a link and the full image is loaded.