Your ancestors are all of the people from whom you are "descended" : your parents, their parents, their parents' parents, and so forth back through the generations.
Because each person has two biological parents, the number of people in your immediate lineage is VERY large : you have 1024 great-great-great-great-great-great-great-great-great grandparents, going back ten generations or about 250 years.
The collection of your ancestors, their siblings, spouses, and offspring, is called your "family tree".
To answer the question "who are my ancestors" you have to do the work yourself, unless you are lucky enough to have a relative who has already done some of the work. There is no great repository listing everyone's ancestors and their relationship to everyone else. Some of the on-line services are trying to get there, but they are still a long way off.
So, you start by asking your parents, grandparents, siblings, aunts, uncles, and cousins what they know about who your ancestors are/were. Then you begin looking at records of births, deaths, marriages, taxes, voting, migration, naturalization, censuses, etc. These begin to tell you the names of the parents of the oldest ancestors you know of. Slowly, with some effort and some blank walls, you will acquire knowledge of a preceding generation, and then the one before that.
This question is unanswerable until a good deal of personal and family information is provided. It usually requires the person asking the question to compile the names, birth dates, birthplaces, migration histories, death dates and places, etc., of their parents, grandparents, uncles, aunts, and other relatives so that someone can research available records.
Direct ancestors follow (are in) your direct line. From you, your direct ancestors would be your:
"On both sides" means your father's side and your mother's side of the family.
Your ancestors are your parents, grandparents, great grandparents, and so on. They are the people you are directly descended from.