When transferring data between systems while some data will map directly you inevitably will come across data objects that need be transformed from the source format into a format that is compatible with the target object. Sitecore Data Exchange framework provides a mechanism and flexibility to reuse to Transform source data objects into the required format for the target data object.
A Value Reader allows you to read a value from a Source object. While it can read the value as is, they can also be used to transform the value. With each version of DEF Sitecore has provided a number Value Readers OOTB.
With DEF version 1.4.1 you have access to the following values readers: