What's an example of a Distributed Database Query?

Since I may not come across or get a chance to use a distributed database system. I would like to understand an example of a Distributed Database Query. I know that in a distributed system, you have database stored on multiple computers connected via network. Basically, I want to know on what level the data is kept on different computer 1. Is it on table-level, database-level etc.? 2. a part of some table is kept on "Computer A" and another part of table is on "Computer B"? If so then Querying the table will take fetching the data from multiple computers.