A "cap table" or capitalization table details the equity ownership and debt obligations of the company. When a VC gives you a term sheet it will include cap table that reflects the post-investment ownership levels of key parties.
In order to prepare the term sheet you will need to provide the VC with your pre-investment (aka pre-money) cap table. This will enable them to make a proposal that balances all of the key considerations: their ownership and the ownership of the entrepreneurs.