What is a Maven artifact?

In general software terms, an "artifact" is something produced by the software development process, whether it be software related documentation or an executable file.

In Maven terminology, the artifact is the resulting output of the maven build, generally a jar or war or other executable file. Artifacts in maven are identified by a coordinate system of groupId, artifactId, and version. Maven uses the groupId, artifactId, and version to identify dependencies (usually other jar files) needed to build and run your code.

An artifact is a file, usually a JAR, that gets deployed to a Maven repository.

A Maven build produces one or more artifacts, such as a compiled JAR and a "sources" JAR.

Each artifact has a group ID (usually a reversed domain name, like com.example.foo), an artifact ID (just a name), and a version string. The three together uniquely identify the artifact.

A project's dependencies are specified as artifacts.

Maven organizes its build in projects.

An artifact in maven is a resource generated by a maven project. Each maven project can have exactly one artifact like a jar, war, ear, etc.
The project's configuration file "pom.xml" describes how the artifact is build, how unit tests are run, etc. Commonly a software project build with maven consists of many maven-projects that build artifacts (e.g. jars) that constitute the product.
E.g.

Root-Project   // produces no artifact, simply triggers the build of the other projects
  App-Project  // The application, that uses the libraries
  Lib1-Project // A project that creates a library (jar)
  Lib2-Project // Another library
  Doc-Project  // A project that generates the user documentation from some resources

Maven artifacts are not limited to java resources. You can generate whatever resource you need. E.g. documentation, project-site, zip-archives, native-libraries, etc.

Each maven project has a unique identifier consiting of [groupId, artifactId, version]. When a maven project requires resources of another project a dependency is configured in it's pom.xml using the above-mentioned identifier. Maven then automatically resolves the dependencies when a build is triggered. The artifacts of the required projects are then loaded either from the local repository, which is a simple directory in your user's home, or from other (remote) repositories specified in you pom.xml.

I know this is an ancient thread but I wanted to add a few nuances.

There are Maven artifacts, repository manager artifacts and then there are Maven Artifacts.

A Maven artifact is just as other commenters/responders say: it is a thing that is spat out by building a Maven project. That could be a .jar file, or a .war file, or a .zip file, or a .dll, or what have you.

A repository manager artifact is a thing that is, well, managed by a repository manager. A repository manager is basically a highly performant naming service for software executables and libraries. A repository manager doesn't care where its artifacts come from (maybe they came from a Maven build, or a local file, or an Ant build, or a by-hand compilation...).

A Maven Artifact is a Java class that represents the kind of "name" that gets dereferenced by a repository manager into a repository manager artifact. When used in this sense, an Artifact is just a glorified name made up of such parts as groupId, artifactId, version, scope, classifier and so on.

To put it all together:

• Your Maven project probably depends on several Artifacts by way of its <dependency> elements.
• Maven interacts with a repository manager to resolve those Artifacts into files by instructing the repository manager to send it some repository manager artifacts that correspond to the internal Artifacts.
• Finally, after resolution, Maven builds your project and produces a Maven artifact. You may choose to "turn this into" a repository manager artifact by, in turn, using whatever tool you like, sending it to the repository manager with enough coordinating information that other people can find it when they ask the repository manager for it.

Hope that helps.