Today marks the first "funnel", one of a few deadlines set in place to keep the legislative process moving. By the end of the day today bills must be passed out of committee from their respective chamber (Ex. Senate files must be passed out of their Senate committee and House files must be passed out of their House committee) in order to continue in the legislative process.
If bills are not passed out, they are considered "dead" and cannot be debated or voted on. Exceptions to this rule are Appropriations bills, Ways and Means bills, government oversight bills, and bills from leadership.