What tool is primarily used for writing scripts in Salesforce to automate processes?

Apex is the primary tool used for writing scripts in Salesforce to automate processes. It is a strongly typed, object-oriented programming language that allows developers to execute flow and transaction control statements on the Salesforce platform's server in conjunction with calls to the API. Apex is particularly powerful for creating complex business logic, enabling developers to write customized solutions that extend standard Salesforce functionalities and automate processes that cannot be handled through point-and-click options.

In contrast, Visualforce is primarily a framework used for building custom user interfaces, while Lightning refers to Salesforce's modern UI framework that encompasses various components and apps for improved user experiences. Flow Builder is a powerful tool for automating business processes without coding, allowing for visually designing the flow of automation, but it does not involve writing scripts like Apex does. Apex is essential for scenarios requiring intricate logic or integration with other systems where advanced programming capabilities are necessary.