You want to understand the theory before you tackle the practical? Here you will find the theoretical basics of Salesforce.
Even though Visualforce is no longer the latest technology, we have collected useful use cases for the Lightning platform.
In the Apex section you will find best practices and interesting use cases for the use of Apex classes.
In the Customizing section you will find step-by-step instructions for configuring your Salesforce instance.
Having a hard time with Lightning Aura/Web Components? Here you will find many examples for a quick start.
Here you will find many examples of how processes can be automated with Process Builder, Workflow, Flows & Triggers.