Archiving refers to the process of storing your data in a long-term storage facility, the version of the data which will be archived should be complete with all data and information used throughout the study. This includes the documentation and metadata which you have created along the way and any other information which would be necessary to interpret and potentially reuse your data.
Archiving research data is a requirement, especially if there is an associated publication. Archiving ensures your results can be verified at a later date. Long term storage for research data is usually located in a repository with a 'lock' placed on the data. This locking ensures the data cannot be edited or altered at a later stage, thus allowing for data integrity to be maintained and for research integrity to be evaluated.
Repositories typically provide a persistent identifier, usually a DOI (Digital Object Identifier). This is a code which can be used to always link back to your data, even if the platform in which it is hosted is altered or changed.