One screenshot explains the entire Salesforce record security model
Often, new Salesforce users find that it is hard to fully understand the Salesforce security model and know what they can control when it comes to record access management. I've created one spreadsheet, which 99% of people know what it is and how it works, to demonstrate how the Salesforce record security model works and what they need to use based on different levels of access control needed.
Leave comments if you think I have missed anything, and feel free to share with others :)