An Artifact is any physical piece of information used or produced by a system, represented in a Deployment Diagram.
Artifacts can have associated properties or operations, and can be instantiated or associated with other Artifacts. Examples of Artifacts include model files, source files, database tables, development deliverables or support documents. The files represented by the Artifact are listed on the Files tab of the element Properties dialog.
To open the files represented by the Artifact, click on the element on the diagram and press ( Ctrl+E ) . Each file is opened either on a separate tab in the Diagram View workspace (if the file can be opened within Enterprise Architect) or in the default Windows viewer/editor for the file type (if the file cannot be opened within Enterprise Architect).
Files can also be launched individually from the Files tab (opening in the Windows default editor), as for elements of any other type that have associated files.
OMG UML Specification
The OMG UML specification (UML Superstructure Specification, v2.1.1, p. 201) states:
An Artifact defined by the user represents a concrete element in the physical world. A particular instance (or 'copy') of an artifact is deployed to a node instance. Artifacts may have composition associations to other artifacts that are nested within it. For instance, a deployment descriptor artifact for a component may be contained within the artifact that implements that component. In that way, the component and its descriptor are deployed to a node instance as one artifact instance.