The upcoming inauguration of Joe Biden is designated as a National Security Special Event, or NSSE. The Department of Homeland Security recently expanded the length of the NSSE for the inauguration to begin on January 13th and run through January 20th.
Here are some links to what it means, and what agencies might be involved in the security and planning of said events:
https://ops.fhwa.dot.gov/publications/fhwahop11012/nsse7_0.htm