|Type of format||Debug|
PDB stands for Program Database, a proprietary file format (developed by Microsoft) for storing debugging information about a program (or, commonly, program modules such as a DLL or EXE). PDB files commonly have a .pdb extension. A PDB file is typically created from source files during compilation. It stores a list of all symbols in a module with their addresses and possibly the name of the file and the line on which the symbol was declared. This symbol information is not stored in the module itself, because it takes up a lot of space.
When a program is debugged, the debugger loads debugging information from the PDB file and uses it to locate symbols or relate current execution state of a program source code. Microsoft Visual Studio uses PDB files as its primary file format for debugging information.
Another use of PDB files is in services that collect crash data from users and relate it to the specific parts of the source code that cause (or are involved in) the crash.
PDB files are usually removed from the programs' distribution package. They are used by developers during debugging to save time and gain insight.
Extracting information 
Although the PDB format is undocumented and proprietary, information can be extracted from a PDB file using the DIA (Debug Interface Access) interfaces, available on Microsoft Windows.