RPL

RPL (Route Policy Language) is an IOS-XR feature that replaces route-maps in IOS-XE. Instead of creating articles about it here, I highly suggest you check out other great resources such as the PDF linked below:

https://learning.nil.com/assets/Tips-/Using-the-IOS-XR-Routing-Policy-Language-for-BGP.pdf

You will get plenty of practice with RPLs as we lab through topics throughout this study guide such as L3VPN and BGP security.