We all experience in the world differently and each of us has our individual microcosms based on our surroundings. The strongest of these surroundings are the people who we interact on a daily basis, family and friends. While we can't choose our family (for the most part), we do have the choice of the friends to be around. (I'm worried if you don't)
We all need friends to at least keep us sane and not feel lonely. For the most part, most of our friends fall into the social category. I have come up with this list to explain the friends that influence me and those that I depend on for specific roles. I use the word 'need' because I would feel lost without a particular friend filling that role.
Your circle of anyone you've met
Most friends fall into the social category. This is anyone you socialize with. Everyone you meet generally falls into this specification. Social friends are your social life, who you go out with to hang out, have fun, and generally just have a good time.
The supportive friend
This type of friend will carry you through your ups and your downs and someone you rely on just to tell you that even when everything falls apart, that it'll be alright. As the term 'rock' implies, this person anchors you down to make sure you don't get washed away in currents of emotion.
Hardline realist and general cynic
When your head is in the clouds and thinking you are invincible, it's necessary to get perspective from someone who will shoot your ego (or your morale) down. You will need someone who's honest (optionally: brutal) who isn't afraid to tell you when you're doing something stupid. My friend who fits this role is cynical to a fault, I make sure I don't take what they say too close to heart on everything. You just want a little reality check, not the doom and gloom of the universe.
Optimist who believes in you
In contrast to the pragmatist, the dreamer believes in you as a person and will support everything you do. This person helps you believe in yourself that no matter how insurmountable something is, they urge you to try it. For me, without my dreamer, I would have given up on a lot of things before I even tried them.
Someone who transforms you
Catalysts are friends that initiate a change in you to be a different person when you are around them. (Hopefully for the better). Some of the catalysts in my life push me to strive to be more driven and competitive such as classmates and peers who show amazing work. There are friends who are more shy and quiet and that changes me into someone who's more sociable than I normally would with other people. The most important type of catalyst for me is someone who challenges me to try new things everyday and be adventurous.
Although I have split these into categories, this isn't to say that you can't have a friend who fills in more than one of these roles, or even all of them. My point is that you should have at least someone to represent each role in your life. You will need to rely on someone who can fill in each role when certain situations arise when life hits you hard. And it will.