How is PDM different than Dropbox or other file-sharing programs?

SOLIDWORKS is a CAD company, and CAD files are complex…Drawings contain Assemblies,
Assemblies contain other Assemblies, which in turn contain Parts. SOLIDWORKS PDM understands and manages those relationships natively, so users don’t end up with broken references when moving, renaming, or interacting with files. PDM can "see" and manage the relationships between files, automatically updating file references and BOMs as needed. PDM also utilizes Workflow to provide true revision (not just version ) control over files, as well as implements a detailed security model to ensure the right people have the right access at the right time. Check-In/Check-Out functions eliminate pesky ‘conflicted copies’ often seen with other file-syncing tools. Finally, SOLIDWORKS PDM is designed as a client/server application, not a hosted cloud service; so your data stays within your company’s network.