Hybrid PACs are political committees with at least two separate bank accounts: (1) a traditional bank account that is subject to all the contribution limitations and source prohibitions, which is then used to make contributions to federal candidates and (2) a separate 'non-contribution' account that may be used to accept unlimited contributions from a wide array of sources for things such as independent expenditures, voter drives, etc.
For more information on Hybrid PACs or how to register a Hybrid PAC, go to the FEC section here:
https://www.fec.gov/help-candidates-and-committees/filing-pac-reports/registering-hybrid-pac/