"Saving" a file is keeping it locally for an undetermined time as it was last saved.
"Preserving" a file is converting a file into an ideal preservation format, verifying its integrity, and storing it in multiple locations with low-access and high-security measures in place to ensure continued access.
Digital Preservation Coalition
by David S. Rosenthal
"Digital preservation is the series of managed activities necessary to ensure continued access to digital materials for as long as necessary. Digital preservation is defined very broadly [...] and refers to all of the actions required to maintain access to digital materials beyond the limits of media failure or technological and organizational change."
--Digital Preservation Handbook, 2nd Edition, http://handbook.dpconline.org/, Digital Preservation Coalition © 2015.
Over time, preservation maintains:
Maintenance occurs through preventative measures, including:
Ideal format properties: