First things first. You can only generate a report for data that exists in your Salesforce organization, unless you purchase Salesforce Connect to connect to an external database, which maps data stored outside into your Salesforce organization; the external data source could also be another Salesforce organization. Your report quality depends on the data quality, cleanness, and completeness. Therefore, system adoption is one of the most important keys to have great data and reports in Salesforce.
Once a report is created, you can store it privately, share with other users, subscribe to notifications when data in the report is changed and meets the conditions set, or schedule it for delivery to yourself and to other users.
In Salesforce, a report is the basic requirement to build a dashboard. Each component in a dashboard needs to have a report...