Schedule K is used to report to partners the income they should include on their personal tax returns. Ordinary income (as determined on page 1 of the 1065) is included on the first line of Schedule K. All other items are items that can be treated differently for each partner depending on their individual tax circumstances. So interest income, dividend income, gains and losses, AMT itmes, charitable contributions, etc, are all items that show up on schedule K.

If you're not familiar, it's probably a good idea, after preparing the rest of the return, to go through schedule K line by line and see if there is anything that needs to be moved from page 1 to schedule K.

Schedule K is the income summary/reconciliation for the 1065. The K-1(s) are a subset of the K. Even if there is no income you'll fill in the K and K-1 with zeros.