You can have a good friend but not trust them with a secret. One of my good friends is a right old gossip. That's just the way she is but she'd always be there if you needed her.
When I was having a hard time with life my best mate came to see me everyday. If I was fine he'd stay 5 minutes. If I wasn't he'd stay until I was. That, to me, is a real friend...
I've had good true friends like that but they are all men. Personally I've found a good female friend is very hard to find. I have one maybe, it's probably me.