How do I know if I will have be given endodontic sealer?

Root canal. If you have root canal therapy on your tooth, then you will have sealer placed in the tooth when they filled the root canal with gutta percha.
Ask your dentist. Most dentist complete root canal treatment with some form of an endodontic sealer. There are quite a few that can be used.
Yes. There are different types of endodontic sealers that are used in conjunction with gutta percha to fill a root canal system. Many dentists have moved towards resin sealers, but some type of sealer will be used.
Ask your dentist. The internet provides a lot of information. Sometimes it is too much. The best thing to do when trying to determine what has happened with your personal dental health is to visit the office where the procedure was completed and request your records. The dentist that completed the procedure or another dentist of your choice can help you to understand what is recorded.