Essentially, the executor's job is to protect the deceased person's property until all debts and taxes have been paid, and see that what's left is transferred to the people who are entitled to it. The law does not require an executor to be a legal or financial expert or to display more than reasonable prudence and judgment, but it does require the highest degree of honesty, impartiality and diligence.
Executors have a number of duties, depending on the complexity of the deceased person's estate.
Figure out who inherits property. If the deceased person left a will, the executor will read it to determine who gets what. Decide whether or not it's legally permissible to transfer certain items immediately to the people named to inherit them, even if probate is required for other property. Find the deceased person's assets and manage them during the probate process, which may take up to a year. This may involve deciding whether to sell real estate or securities owned by the deceased person.