You know, friendships are a really strange thing. They come in many different forms.
Standard Friends: Your regular, every day average joe friend. You enjoy their company, and enjoy hanging out with them every now and then. However, they are not those that you would immediately think to turn to in an emergency.
Best Friend: This is usually the one (Or in some cases more) people that you trust unconditionally. You exponentially enjoy their company, and feel like you can rely on them for just about anything. When you are in trouble, these are the people you trust to have your back. They also are the people that you trust to inform you of when you are acting/doing something wrong.
Previously Dated: These people are the people of whom you were once romantically involved with. You each know many different things, secrets about each other. However, more often than not these friendships fall apart after one partner breaks it off with the other. They grow distant, sometimes forever as they each move on with their lives.
Previously Dated (Best Friends): This is a rare, but incredibly unique friendship. More often than not, two people grow distant once their relationship ends. Every so often though, it actually makes the friendship stronger. If two people really value the other person, they will work through their troubles to stick around. They trust each other without question, and their bond is something that is not easily defined or understood by others.
Dependant Friends: These are the friends that look to you for help and advice simply because they have nobody else to turn to. Whether it be because they have no other friends in the area, or do not have any other close friends they can spend time with easily, they will often turn to you. They will often be very open to you without much hesitation. They feel comfortable telling you whatever is on their mind simply because they know you will listen.
There are many others I wish I had time to define, but my laptop is dying so I have to post this quickly. Ha ha!
It is really interesting to see what kinds of friendships everybody forms, and who fits into what catagory in your own life.