I and my wife are 80 years old and have outlived our savings. Our only income is our social security. One of our creditors is about to file a judgement, whatever that is. Can they somehow attach our social security payments? What else can we expect to happen? We do own our home with a mortgage about equal to the mortgage.

They don't file a judgment. They file suit against you to obtain a judgement. A judgment is a ruling by a court that you owe them money and they can use legal means to recover that money. However, social security payments are exempt for garnishment. But you need to inform your bank that your only deposits are from social security payments and therefore exempt from attachments. Otherwise they can attach your bank account.

You may be a candidate for a reverse mortgage by the way.

This is not your situation as you write it, but thought I would add this from ssa.gov:

Social Security will garnish benefits:

To enforce child support or alimony obligations under 42 USC 659;
To enforce a valid garnishment for court-ordered victim restitution under 18 USC 3613;
To collect unpaid Federal taxes under 26 USC 6334(c);
To have a portion of your check withheld to satisfy a current year Federal income tax liability under 26 USC 3402 (P); or
Other Federal agencies will offset benefits to collect money from benefits to pay a non-tax debt owed to that agency according to the Debt Collection Act of 1996 (Public Law 104-134).

What does it mean to have 'a mortgage about equal to the mortgage?'