A repository is a tool to share, preserve, and discover research outputs, including but not limited to data or datasets. While workflows and processes will vary across repositories, generally speaking, researchers submit and describe their own data which is then ingested into the repository for storage. Other researchers can then download, or request to download, the data directly from the repository.
There are several types of repositories, including but not limited to institutional repositories, generalist repositories, and subject-specific repositories. Institutional repositories are generally managed and financed by an academic institution for use by its researchers and their colleagues. Subject-specific repositories are designed to fit the needs of specific research fields and the data they produce. Generalist repositories are intended to store and render findable any data from any field.
NIH Open Domain-Specific Data Sharing Repositories:
Resources like re3data.org can help you locate a repository, to either deposit your own data or to search for data for re-use or secondary analysis.