Shared Albums from others

I sometimes get albums shared from others that may have hundreds of photos in them. If I accept these albums does it fill up my iCloud space and may ultimately require me to pay for more storage? What is the best way to handle this? If you look at the photos, do they automatically go to your cloud? Or could I select a few I like and save to my own photos? I have just not joined in the sharing because of not knowing…

I now finally understand that I can organize my own photos into albums without taking up more memory or cloud space. I was so happy to know this and wish it had been made clearer from the get-go!