I think a true friend refers to someone who stands by you when the world is against you

I would say it means a friend who really cares about you and whom you can trust to stay with you, no matter what happens.

A friend who stays with you and has your best interests at heart, in good times and bad.

A true friend is the person who is always there when we have need without nothing demanded in return. this is that who console you when you are in the pain. this is a person very rare. When we have a true friend we have a tresure !

I agree with the other comments and would add that there are some people who may pretend to be your friend but prove not to be "true" friends in times of trouble or hardship. Those "false" friends will desert you and leave you to deal with those troubles alone.