what is a Friendship

A group of friends consists of two or more people who are in a mutually pleasing relationship engendering a sentiment of camaraderie, exclusivity, and mutual trust. There are varying degrees of "closeness" between friends.
Friendship is considered one of the central human experiences, and has been sanctified by all major religions. The Epic of Gilgamesh, a Babylonian poem that is among the earliest known literary works in history.
In a comparison of personal relationships, friendship is considered to be closer than association, although there is a range of degrees of intimacy in both friendships and associations.
Types of friendships
Best friend is a person(s) with whom someone shares extremely strong interpersonal ties with as a friend.
Acquaintance is similar to a friend, but sharing of emotional ties aren't present. An example would be a coworker with whom you enjoy eating lunch, but would not look to for emotional support.
Romantic Frienship is the very close but non-sexual friendship shared between two friends, often involving physical contact such as hugging, holding hands, and even cuddling.
Soulmate: the name given to someone who is considered the ultimate, true, and eternal half of the other's soul, in which the two are and forever were meant to be together.

Pen pal is a person who shares a "postal" relationship with another and regularly writes via "snail mail". They may or may not have met each other in person and may share either love, friendship, or simply an acquaintence between each other.

Internet friendship is a widely debated and form of friendship or romance which takes place over the Internet.

Comrade is means "ally", "friend", or "colleague" in a military or (usually) left-wing political connotation. This is the feeling of affinity that draws people together in time of war or when people have a mutual enemy or even a common goal. Friendship can be mistaken for comradeship.

As a war ends, or a common enemy recedes, many comrades return to being strangers, who lack friendship and have little in common.

Casual relationship is the sexual or near-sexual and emotional relationship between two people who don't expect or demand to share a formal romantic relationship. In the U.S., this is considered "a fling".

Boston marriage is a term used in the nineteenth and twentieth centuries to denote two women that lived together in the same household independent of male support. Relationships were not necessarily sexual. It was used to quell fears of lesbians after World War I.

Blood brother or blood sister is may refer to people related by birth, or a circle of friends who swear loyalty by mingling the blood of each member together.