The document discusses how Twitter is being used before and after its introduction and how it can be incorporated into personal learning environments (PLEs) and networks (PLNs) for language teachers and learners. It outlines the differences between PLEs, PLNs, and virtual learning environments (VLEs) and some benefits of PLEs, such as access to a global audience and diverse viewpoints. The document also addresses barriers to teacher adoption of Twitter and provides examples of how Twitter can be used to introduce learners to social networking and language learning through interaction and self-help.