In simplistic terms, OneDrive is a cloud based app that comes with your O365 suite of apps that you can use to share files with individuals inside our organization.
To use OneDrive, login to O365: http://mail.office365.com
Then choose OneDrive under your Apps:
You can upload and share files with anyone in our CCSF organization. So then why not just attach the files and send it via your O365 or SFGov Outlook email? Remember, the maximum size on any given attachment per email is 25 MB (megabytes). So if you want to share a file that is 25 MB or larger, OneDrive would be the way to go.
For OneDrive for Business Desktop see attached.
See also:
OneDrive basics video