Your online reputation is what people online think about you. If you do positive things and behave with respect, then your reputation will be positive. You may get a negative reputation if you behave badly and do things to upset other people or if other people share things about you online that make you look bad.
An online reputation gives a first impression of who you are – if you are making new friends, they might look up your online history, your school might search for you online, and later on in life, companies and employers search for people online and would rather give a job to someone with a positive online reputation than a negative one!
Remember, the things you post and share online can stay online for other people to see for a very long time, sometimes even years!