The nitty gritty is here: https://bidenwhitehouse.archives.gov/wp-content/uploads/2023...

The infographics version is here: https://www.cbo.gov/publication/61181

The TLDR is: Social Security, Interest payments, Medicare, Defense, Medicaid, Income Security Programs, and then a whole hodgepodge of Other. Politicians can try to cut a bit in Other or maybe Income Security, but the other big blocks are nearly untouchable Third Rails.