UML Class describes a type of object, a concept that describes a state (attributes) and behavior (methods). The only mandatory information is the class name, the attributes are written under the class name and separated by a line from the methods. The classes are used to create objects in object-oriented design.
A class can be engaged in one or more relationships with other classes. There are different relationship types, such as association, composition, aggregation, etc. You can demonstrate an association relationship between classes using Gleek.
Gleek uses an informal UML diagramming language with its own syntax. If your goal is to create perfect class diagrams, Gleek might not be for you. If your goal is to communicate your idea, Gleek will help you to quickly generate diagrams during a meeting or when collaborating.