The Map Transform allows you to setup a map of input values to output values. Inputs can be anything from specific values or strings, to numeric ranges of values. Each input value can then be mapped to an output value, such as a string, integer, color, style, etc. A great example of this is mapping values to colors, so that you can easily show state changes.
The Format Transform applies a format string to the value returned from the binding, allowing you to format the output in any way. The format can be something like a date format or a number format.
The Script Transform will run a script that allows you to manipulate the value returned from the binding using any Python script you want.
The Expression Transform runs an expression on the original value so you can manipulate it without creating more complex logic. This is most useful when you are indirectly binding to a Tag but still want to apply an expression to it, it can now be done in two distinct steps.