Authoring is the term used to describe the ability to change the content in a CALL computer program.
For example, some off-the-shelf CALL programs come supplied with a bank of questions in English. However, these may not quite be suitable for a class in terms of level and content.
An authorable program, however, will allow the teacher to write their own questions and set different levels, etc. These questions, incidentally, can often include not just text but also sound, video and so on.
So quite simply, when you are choosing CALL programs for your school you need to make sure that whatever programs you finally use are all authorable. You don’t want to be restricted to the questions and content the original program think you want, you want to be able to decide for yourself what is best for your students.