Skip succinctly summed it up. One thing to keep in mind if you are current on your mortgage, you may have a different experience than if you are delinquent. Why I mention this is that in Illinois, the lender has the legal right to proceed with foreclosure once you have missed 3 payments and you do not have a signed and executed loan modification in place.
Also, when you call your existing mortgage company, ask for the modification department.
PahRoo Appraisal & Consultancy
Read the state of Illinois warning about loan modification scams: