LightRocket allows you to set access to your files, determining what type of user can view and/or download your work (depending on the permissions granted). You can access this feature by selecting files in the file viewer in your My Files panel, clicking on the 'Visibility' menu option and then selecting 'Restrict access'. See screenshot below.
You have the option to either make a searchable file accessible by default for public access or you can limit access to either 'personal' or 'professional' contacts - using the 'Restrict access' feature.
There is no difference between files that are marked as 'personal' or 'professional' other than that searchable files for which access has been set in this way will only be visible and/or downloadable by contacts who have been granted corresponding 'personal' or 'professional' rights.
So if you mark a file, or files, as 'personal' only your contacts classified as 'personal' will be able to see and/or download (depending on the permissions granted) those files.
Similarly if you mark a files, or files, as 'professional' then only contacts you have classified as 'professional' will be able to see and/or download (depending on the permissions granted) those files.
The purpose of this feature is so you can upload a bunch of personal pictures, make them searchable on your site and/or LightRocket and then set access so only contacts who have been classified as personal will be able to see those files, leaving you in control of who can see your work and ensuring you have privacy when you need it.
The 'Set Access' screen looks like this: