According to wikipedia: "Contact improvisation is a dance technique in which points of physical contact provide the starting point for exploration through movement improvisation. Contact Improvisation is a form of dance improvisation and is one of the best-known and most characteristic forms of postmodern dance."
Mostly this means that the dance revolves around the sensation of physical touch. It can have elements of ballroom dance, light martial arts, body work, and other modalities. It was the first dance to have women lifting men, and tends to be more gender equal than some other dance forms. There is no leader, nor follower in the dance, and so having duets with the same gendered person is common place.
Below is an example of two talented dancers. This is an example of "technical" Contact Improvisaion. While this is the style taught in classes around the world, it is not the only way to dance Contact Improv, and freedom of expression tends to be highly valued. Contact Improv can be silly, cathartic, restful, playful... it depends on each dancer in the moment!
Being humans, sexuality will almost always come up for people in many different settings. Contact Improv, being focused on touch, can bring up these feelings for many people. In a society that rarely touches, except as lovers, Contact Improv can bring up these feelings, especially for those not used to so much physical contact. It is normal for people new to the form to feel as though a lot of sexuality is occuring in the dance. Seasoned dancers tend to build up more destinctions in touch and tend to have less sexuality in their dances.
While sexuality may come up as an experience, we greatly recomment that sexual expression be left off the dance floor. If you feel the need for sexual expression to another person, we recommend that you check in and use words ("I feel ____, what is going on for you?") instead of any physical expression. For more information on sexuality in dance, please see our guidelines.
While sexuality is not recommended in the dance, sensuality, or delighting in the senses is encouraged. Pleasure from the sensation of physical touch and connection with another person can be great ways to enjoy Contact Improv. The video below seems to me to be a celebration of the sensual connection of Contact Improv: