DIN 41622 connectors are named for Deutsches Institut für Normung, the German company who first standardised these types of connections. This type of DIN connector are generally used in broadcast audio, for terminating multipair audio cables in particular. They can be used in wiring between studios, and connecting to rack-mounted equipment. DIN 41622 connectors are similar to DIN 41618 connectors, but have a lower pin density, with 30 pins compared to 39.
DIN connectors are usually associated with audio applications, which is the purpose that they were first standardised for. Each number corresponds to a connector with a different configuration of pins, and each has a specific use. There are many configurations, which makes them a very popular and versatile type of connection.
DIN 41622 connectors come in a range of different formats, with the connector having different potential genders, rows, and numbers of contacts. This will dictate what they are used for, as you may require more or less contacts and rows for a given connection.