PHsPeed is component-oriented. That means that you can pick a component from the component toolbar and put it on your form. Examples of components are 'an edit box', 'a checkbox', 'a grid'. As these components are part of the user interface, they are called 'visual components'. That implies that there are invisible components, and that's true. Examples of that are database connectors, data sources, tables and more.
Each component has 'properties'. Those are special variables to influence the standard behavior. If you put an edit field on the form then the edit field will have a default behavior. Suppose you want to make the field required so that it cannot contain an empty value. Then you set a property 'required' to 'true'. When you generate the application, you will see that the field is mandatory.
CSS is needed for the look and feel of your application. It too is generated on the fly. Sometimes by code, sometimes out of a style sheet. It depends. A lot of the CSS is hidden behind the Bootstrap framework.
In the integrated development environment (IDE) you design your forms, (add custom code to events), generate, test, and deploy your code. PHsPeed has a lot of tools to make that process even easier as it can generate full working applications based upon a database table. The form designer is used to make a conceptual drawing of your form. As the real presentation depends on the device you are using for display, a real Wysiwyg is not applicable. However, to generate and run the application takes only a few seconds, and then you can see the result live. By setting the size of the viewport, you can emulate large screens to small mobile devices.
Working with PHsPeed fits in many development approaches including the agile (scrum) approach. See here.
But if you prefer prototyping, DSDM, or other methods, then you will see that PHsPeed will fit into that too.
The first step could be to download and install the software and use the evaluation period to see if the product is for you. Although PHsPeed is a low-code platform, it does not mean that you never have to write code. But it's minimal. So if you are not a real developer, then you are most likely able to create simple applications or prototypes. For more complex business rules, however, you will need to write code, or find someone who does that for you. However, as you can always create a significant part of the application yourself, you save money by letting only the programmer do work that you can't.