New "Local Items" Keychain in macOS 10.9+: What's it all about?
If you mean the keychain that is called Local Items in the U.S. English locale, I think it is used for keychain items that are eligible to be synced with iCloud Keychain.

From http://arstechnica.com/apple/2013/10/os-x-10-9/5/:


  If the iCloud Keychain is subsequently disabled, the iCloud keychain highlighted in the screenshot above is replaced with a "Local Items" keychain that has the same contents as the iCloud keychain. Any items added to the Local Items keychain will be pushed out to other devices when iCloud Keychain is re-enabled.


I have never enabled iCloud Keychain, but I also have a Local Items keychain. It contains about half of the keychain items from my login keychain, or mostly web form passwords. The Local Items keychain does not seem to correspond to any file and it cannot be deleted.