Hi @Musician and Editor; welcome to the Community and thanks for using Dropbox!
When you download and install the desktop app on a computer, a Dropbox Folder is created which hosts your accounts content.
Since syncing is one of our core features, any changes you make within your Dropbox folder will sync across your connected devices and the website. This won't be affecting files that are outside your Dropbox folder though.
For more information about this, you can also have a look at this discussion as it seems to echo your query.
Let me know if you have any more questions.