What's a practical use of .PDB files?

I have been reading about PDB files and how they have to do with debugging but why would I want to keep a pdb file after I ship? If there is a problem, I can just debug on my machine. What am I missing?

PDB files contain debugging information. If you keep them around at least for released versions of your software, you can debug any crashes a customer may have. You don't need to send them the PDB, simply have them collect a crash dump (.dmp) using Windows. Then, you can open up the dump in for example WinDbg and debug the issue.