Difference between two contacts folders

I have 2 contacts folder as seen below. What’s the difference? there’s data in both but not
the same. what’s card vs local?  Why 2 categories? which one should I use?

Hi, the “card” folder contains data from your mail (contacts) service, i.e. this folder is synchronized with the server and all the data available in eM Client for this folder, should be automatically synchronized wherever you setup the account.

Local folders however contain only local information, e.g. stored on your computer. These contacts won’t be synchronized with any of your devices nor with the server and in case there’s an issue with your computer for example, without a backup, you might lose this data.

Hope this helps,