The probate process occurs after your death. It is a court case that will handle various issues or tasks involved in closing your estate.
To guide the process on your behalf, you will either have an executor or an administrator. These roles are exactly the same, but there is one key difference.
An executor is someone you choose and appoint before your death. If you had an estate plan, then you will have an executor.
An administrator is a person appointed by the court after your death. You will have an administrator in your probate case if you did not have an estate plan, did not appoint an executor or if your executor is somehow unable to carry out the duties of the position.
Beyond the detail about who appoints the representative, both executors and administrators have the same job duties. They will help guide your estate to the closing by finding heirs, alerting creditors, managing assets and handling paperwork. The person will also deal with any issues and help the court finalize your case. The court will supervise the person as well, regardless of whether it is someone you appointed or who the court chose.
If you did not have an estate plan and appoint an executor, there may be no need for the court to appoint an administrator. Some estates will not need to go through probate because you do not have a lot of assets or most of your estate already legally passes to heirs through beneficiary accounts, trusts or other means, and an administrator is only necessary for the probate process. In this situation, the person who will usually inherit the bulk of your estate will manage the process of closing it out.