What does the cloud icon with arrow mean on my MacBook?

Hi, All the folders on my Macbook iCloud have a cloud with an arrow facing down. Every time I connect my MacBook to the internet I download these files and in the next session the cloud with an arrow facing down comes up on all the Folders again. I have been doing this for weeks now. I have researched on the internet and it says that the files are available online only hence the first time I need to have data connection to be able to access these. I would like to change this.

Additionally, if I add a new file on my Macbook I would like it to automatically sync with iCloud.

Can you please help me? Thank you ever so much!!

[Re-Titled by Moderator]