Most of us really don't have a very good idea of what the executor of an estate really does. The essence of the job is to carry out the deceased person's wishes--to collect the person's assets, pay debts and taxes, and distribute what's left to the people or institutions the person wanted to inherit it.
Because an executor is in charge of someone else's money, the law imposes a high ethical standard. An executor (also called personal representative) must be completely honest and always act in the best interests of the estate. You must also deal with the people who inherit under the terms of a will or, if there isn't a will, under state law. And if necessary, you must shepherd the estate through probate court proceedings, probably with the help of a lawyer and other experts.
If that sounds daunting, it's understandable. But the truth is that you don't have to have expertise in finance, tax, or law to be a good executor. You just need to be honest, conscientious, and willing to take the time to deal with a lot of paperwork and detail. If you need expert advice, you can hire professionals, and pay them from estate assets.