From an assessment/exam perspective,  Bloom's Taxonomy is a set of hierarchical skills that need to be demonstrated when it comes to extended writing.  These skills are linked to a set of command terms that are asked across all subjects. 

You start at the bottom of the hierarchy where you need to answer low order thinking skills questions such as list/state/identify. Here you are demonstrating your knowledge and understanding of concepts/topics.  As you move up the hierarchy, the skills you need to demonstrate get more and more challenging where you need to be able to answer questions that begin with command terms such as describe/ explain/compare and contrast. 

Towards the top of the hierarchy, you come across higher order thinking skills such as analysis and evaluation.  When students have to do this, questions will begin with words such as discuss/recommend/justify.These are some of the hardest skills to demonstrate which is why they will have the highest marks in an exam.