Homophobia is when someone says something mean or hurtful against anyone who isn’t straight, or says anything about anything being gay that is disrespectful or offensive even if it isn’t directed at anyone, or treats you differently because of your sexuality.
Homophobia is never ok, and you should not have to face any kind of discrimination (discrimination means people treating you differently or negatively because of something about you) because of your sexuality. If you are upset by the way someone is treating you, you can speak out about it. If it is someone at school then you could tell a teacher, or if it is someone being dangerous or threatening towards you then you could tell the Police. If it is someone in your personal life that is the problem, consider whether that is the sort of person you want in your life? If you have to have this person in your life, it could be worth trying to have an open and honest conversation about their homophobia if you feel like they are the sort of person who is open enough for that.