Using Parameters in your queries can help make them safer (less likely to be injection attacked), and easier to define logic than in a single WHERE condition. These tools add a parameterized version of the Custom Query Web Parts, allowing you to define fields that match your Custom Query's Parameters and pass values easily.
These Parameterized Custom Queries Web Parts operate much like the Transformable Web Part, allowing you to clone the web part, and then define properties in your new web part. These properties will automatically translate into Query parameters that your Custom Queries can use!
Combine with Macros (such as Query String Macros) to make your own APIs or easy to use filters on your repeaters and listings!