JCR (Java Content Repository) is a java interface used to access contents that are not only web contents, but also other hierarchically stored data. The content is stored in a repository. The repository can be a file system, a relational database or an XML document. The internal structure of JCR data looks similar to an XML document, that means a document tree with nodes and data, but with a small difference, in JCR the data are stored in "property items".

Or better to cite the specification of JCR: "A content repository is a high-level information management system that is a superset of traditional data repositories."