Overload

Students often complain about being overwhelmed and perhaps with good reason. Many instructors were educated at a time when there was a strongly defined, relatively static core of knowledge required for graduation. Instructors apply this model of core knowledge to their instructional design. The core in this Internet age, however, is expanding and changing so rapidly for many disciplines that knowledge held as orthodoxy, even as recently as five years ago, may now be questionable, if not wrong. In addition, new technology critical to the process of working and learning is constantly being developed. The Information Technology students encounter at the beginning of their college education can be obsolete by the time they graduate. This creates extra demands on the finite processing abilities of their brains.
 
Cognitive load theory addresses this issue and has been an influence on many educational theorists. The theory divides load on our cognitive processing abilities into three parts: intrinsic, germane and extraneous. Intrinsic load is specific to what you are trying to achieve, germane is the parts of the intrinsic load that especially triggers new schema (patterns of understanding) and extraneous is all the things you have to process in order to get to the intrinsic and germane.

Here John Sweller one of the main proponents of the theory talks about extraneous load:

A good example of extraneous load is learning to operate a software application used in teaching. It is not intrinsic to what you want students to learn since operating it has no value in itself, but it may be necessary to get to the germane load. The more complex interface to the technology the greater the extraneous load, the more intuitive the user interface the lower the extraneous load. This is why usability is an especially important factor in the design or evaluation of educational software.

Researchers in education use cognitive load theory to seek ways of redesigning instruction to reduce extraneous load and be more focused on germane load. A user-centred approach to design and evaluation of technology and language used in education is very important in reducing cognitive load and therefore maximizing learning. It is also important not to make too many assumptions about the processing level of your students and to even out the load across a course. 
 
Reference

Sweller, J., Van Merriënboer, J., & Paas, F. (1998). “Cognitive architecture and instructional design”. Educational Psychology Review 10 (3): 251–296.