Every entry into your house that is used should have an outside mat that is rough enough to remove mud, debris and soil. Your inside entry should have a mat that is absorbent and can remove any moisture.
The outside mat should be able to withstand the elements and have someplace for the dirt to drop into so that it does not get contaminated and start doing the opposite of what it was intended to do.
The inside mat should be heavy enough to lay flat and have a rubberized back to prevent creeping. These mats should be small and light enough to be able to be cleaned regularly - they are the heart of prevention!