What is purpose of the [CLS] token and why is its encoding output important? I am reading this article on how to use BERT by Jay Alammar and I understand things up until:


  For sentence classification, we’re only only interested in BERT’s output for the [CLS] token, so we select that slice of the cube and discard everything else.


I have read this topic, but still have some questions:

Isn't the [CLS] token at the very beginning of each sentence? Why is that "we are only interested in BERT's output for the [CLS] token"? Can anyone help me get my head around this? Thanks!
CLS stands for classification and its there to represent sentence-level classification.
In short in order to make pooling scheme of BERT work this tag was introduced. I suggest reading up on this blog where this is also covered in detail.