The Module Designer allows you to create or extend the functionality of an existing module within Vtiger CRM. If you are not aware of what a module is within Vtiger, these are the sections of the CRM where individual record types are segmented, created, and stored. These include Contacts, Organizations, Deals, Invoices, and many more. These type of modules are called Entity modules, which supports out-of-the box features like Reports, Workflows, Approvals etc.
We also support modules that do not follow these standard conventions, such modules are helper modules supporting core modules to achieve specializations. For example Sales Insights, they shows analytics from Deal modules, Keyboard shortcuts giving you quick ways to perform day today activities using just your computer keyboard. These types of modules are called Extension modules.