Exploitation is the way a teacher or learner uses resources to meet their learning aims.
A teacher can exploit a native speaker by asking them to come into the class and talk to learners, asking learners to prepare interview questions beforehand or by using the native speaker in a role-play, etc.
In the classroom
One interesting area many teachers explore is finding new ways to exploit the course books prescribed for their classes. Few course books are suitable for every learner and finding new approaches to material in them based on learner needs is a useful skill.