A Use relationship indicates that one element requires another to perform some interaction. The Use (or Usage) relationship does not specify how the target supplier is used, other than that the source client uses it in definition or implementation. A Use relationship is a sub-typed Dependency relationship.

You typically use the Use relationship in Use Case diagrams to model how Actors use system functionality (Use Cases), or to illustrate usage dependencies between Classes or Components.

Note: it is more usual (and correct UML) to have an  Association Connector between an Actor and a Use Case.

Note: To depict a usage dependency on a Class or Component diagram, draw a Dependency connector. Right-click on the Dependency, and select the Dependency Stereotypes | Use menu option.

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OMG UML Specification

The OMG UML specification (UML Superstructure Specification, v2.0, p. 111) states:

"A usage is a relationship in which one element requires another element (or set of elements) for its full implementation or operation. In the metamodel, a Usage is a Dependency in which the client requires the presence of the supplier."