What is a credit carryover?

[LindaA]

A credit carryover is when the unused portion of a nonrefundable credit is carried over to the next tax year. In other words, the amount of the credit you can't use on your current tax return can be used next year's tax return. For example, if you claim an energy credit in the current year but are unable to use it, you may carry it forward to the next year, as discussed in the FAQ below. TurboTax will automatically carry forward a credit for you if a carryover is allowed for that particular credit.

Why is my Home Energy Credit being carried forward to next year?    https://ttlc.intuit.com/replies/5521524

[tarver810]

I think I understand, thanks for your help