Comparing CALLS to materials' for language learning/teaching (course books, dictionaries etc..) , we can say that
Both involve something physical that teachers and learners use alongside a teaching method, syllabus etc. in a taught program OR which may be just used independently by the learner.
. Both have to be bought (or pirated .
Both have a tangible form, but at the same time when exploited form part of a less tangible 'task' or the like.