"What's right isn't always popular. What's popular isn't always right".  

What this quote means is that the right thing to do isn't always the common thing to do or is something that is done rarely. What everyone mostly does is more common than what is the right thing to do. For example, lets say you're cheating on a test you already know that it's wrong but you say to yourself "well if everyone else is doing it then why not." That is more popular than doing what the right thing is. If you are not cheating then that is less likely what other people will do. In some situations there are no other choice but to choose what's right or what is popular. But it isn't ok to always choose what's popular. You shouldn't be a follower. You should choose your own way. If you see some other people who are choosing the wrong and looks fun, you shouldn't go ahead and do it also to fit in. You are born to stand out.