What does "did you pay more than half the cost to keep up your home in 2020" mean?

It means did you pay more than half of the cost of keeping up a home for the year in order to file as Head of Household.

The IRS provides a worksheet in Publication 17, Your Federal Income Tax, which lists the common costs for keeping up a home, and allows you to track whether you have paid over half of the costs here. 

Costs you include. Include in the cost of keeping up a home expenses, such as rent, mortgage interest, real estate taxes, insurance on the home, repairs, utilities, and food eaten in the home.

Costs you don’t include. Don’t include the costs of clothing, education, medical treatment, vacations, life insurance, or transportation. Also don’t include the rental value of a home you own or the value of your services or those of a member of your household.