Real Dictionary

liaison
If someone acts as liaison with a particular group, or between two or more groups, their job is to encourage co-operation and the exchange of information.
countable noun: You can refer to a sexual or romantic relationship between two people as a liaison.
uncountable noun: Liaison is co-operation and the exchange of information between different organizations or between different sections of an organization.

liaison in American English
a linking up or connecting of two or more separate entities or of the parts, as military units, of a whole so that they can work together effectively
noun: the contact or connection maintained by communications between units of the armed forces or of any other organization in order to ensure concerted action, cooperation, etc

liaison in British English
noun: communication and contact between groups or units