I'll try to make this as simple as I can because the at-risk rules are very complicated in practice but really don't apply to most normal taxpayers. This information also wouldn't be found on any of your forms.
A good rule of thumb is if you don't know what it means - then its almost certainly "All investment is at risk."
Basically, if your business were to fail or lose money and you would personally lose money, then your investment is at-risk. If you would not personally lose any money even if your business failed because someone else is guaranteeing your investment or through a non-recourse loan, then your investment is not at-risk. The reason you need to make this distinction is that the IRS will not allow you to take a loss on your Schedule C if you are not at-risk of actually losing any money.
See this TurboTax article for further explanation -
https://ttlc.intuit.com/replies/5205776
