With more than 4 million homeowners behind on their mortgage payments, the government and major banks are scrambling to help at-risk borrowers avoid foreclosure.

What exactly have they done—and can they do more?

For one thing, the government and the mortgage industry said Tuesday a new plan will allow lenders to alter delinquent loans more quickly. That follows Citigroup’s announcement late Monday that it would expand its efforts to help its beleaguered borrowers. Other national banks have initiated similar programs.

But what else is on the table?

Here are some questions and answers about mortgage assistance:

Q: What is a foreclosure moratorium?

A: A foreclosure moratorium is when a lender holds off on starting a foreclosure or completing a foreclosure sale on a delinquent borrower, to give both parties time to rework the loan or set up a repayment plan.

Oftentimes, the lender sets conditions for a moratorium. They might require, for example, that the home be the borrower’s primary residence and that the borrower have enough income to make affordable mortgage payments.

Q: What is a repayment plan?

A: When a lender works out a plan for a borrower to pay back missed payments, it’s called a repayment plan, or forbearance. A lender can increase the monthly payment until the missed payments are paid off or add the missed payments to the total principal the borrower owes.

Q: Can a restructured mortgage include an interest rate reduction?

A: Yes — to lower monthly payments, a lender might decrease the mortgage interest rate either permanently or temporarily.

Q: What is a principal reduction?

A: A principal reduction, or forgiveness, lowers the total principal amount the borrower owes on the mortgage. That, in turn, decreases the monthly payment.

Q: How can changing the length of the loan help a struggling borrower?

A: To lower payments without changing the interest rate, a lender can extend the time required to pay off the loan. For example, a lender might restructure a 30-year mortgage as a 40-year loan, shrinking the payments by stretching them over an extra 10 years.

Q: Who else can help borrowers?

A: Borrowers are encouraged to contact their lenders or mortgage servicers as soon as they think they may fall behind on a payment. The sooner contact is made, the easier it is to head off larger problems.

Homeowners can also contact a nonprofit housing or credit counseling service to help with lender negotiations. Reputable services can be found, state-by-state, on the Department of Housing and Urban Development’s Web site, and the Homeownership Preservation Foundation has a 24/7 toll-free hot line: 888-995-HOPE (4673).