A mixer party is often an informal gathering where people mingle, interact and get to know one another. Common activities at mixers may include dancing, playing games, socializing and drinking. Most mixer activities are designed to allow free interaction between the party-goers.
In some cases, mixers are held to allow members of separate groups to socialize. For example, it's common for fraternities and sororities to throw a mixer so that members of their respective groups can become acquainted. Similarly, mixers are often held so that single people may meet other singles who are interested in dating or beginning a relationship.