Free vs Pro version

Hello, I recently came across your color app so I'm trying it out. Your site says most features are free to use but to upgrade to the pro plan if we need more. What does "more" entail? Is it the additional high res export options or are there other features added? I also saw that it said we could install the app on our desktop. I don't see the button to install as shown in the picture. Is this a paid feature? Thanks!