Snapshots allow you to re-run a query used previously. The Snapshot system automatically keeps a record of all the Research and Optimize queries that were run. Selecting a Snapshot starts a new run of the query, so you will always get fresh data.
The Snapshot system does not cache any results. It only stores the topic, page (if applicable), country, language, date, application, and username. Note that the Research Snapshot also stores the optional URL if one was entered.
Snapshots are saved across the entire organization. Any user on the account will see any query run account wide.