System Files Extensions - What are system files and how do I open a system file?

What are system files and how do I open a system file?

File Type Category File Format
.adm System Files Administrative Template File
.bcd System Files Windows Boot Configuration Data File
.chg System Files Windows Net Logon File
.clb System Files COM+ Catalog File
.diagcab System Files Troubleshooting Pack Cabinet File
.diagpkg System Files Troubleshooting Pack File
.ffl System Files Find Fast Document List
.ffo System Files Find Fast Document Properties Cache
.fid System Files Microsoft Catalog Indexing Service File
.msc System Files Microsoft Management Console Snap-in Control File
.msp System Files Windows Installer Patch
.pfx System Files PKCS #12 Certificate File
.scb System Files Scrambls Encrypted File
.spl System Files Windows Print Spool File