Reindexing and One Stop indexer.

I need some help with these two different tasks in XC. Here is my current understanding of them.

Reindexing
1. Reindex totally indexes all the records over again for all the metadata records coming from the same source.
2. The functions are defined in xc_index.module.
3. The reindex uses xc_solr_xc_store($data, $locations); in order to store metadata into Solr

One Stop Indexer
1. One Stop Indexer works by indexing all the records that have been harvested or haven't been indexed.
2. It is defined in xc_solr.module.
3. It re indexes using xc_solr_metadata_to_solr_iterate_indexes() from xc_solr.index.inc

Please let me know which one should be used for what purposes.