Since you have a Schedule K-1, you have an investment in either a partnership or an S-Corporation.
If you can lose what you paid ("invested") for your share of the partnership or S-Corporation (e.g. through operating losses, bankruptcy), your investment is "at risk".
If you didn't pay anything for your share of the partnership or S-Corporation, or have a guarantee that you won't suffer any financial losses, your investment is not "at risk"