I have been using Apple's dictionary app on my Mac, could someone tell me what the formal name of the characters are next to word 'Causation' in the screenshot and what is their purpose?
The entire collection is called the International Phonetic Alphabet.
The IPA is the major as well as the oldest representative organisation for phoneticians ... 2013 marked the 125th anniversary of the first publication of the International Phonetic Alphabet and the formulation of the principles.
The aim of the IPA is to promote the scientific study of phonetics and the various practical applications of that science. In furtherance of this aim, the IPA provides the academic community world-wide with a notational standard for the phonetic representation of all languages - the International Phonetic Alphabet (also IPA). The latest version of the IPA Alphabet was published in 2005.
Note that different languages require a different subset of the symbols. In fact different dialects within a single language may be catered for, e.g.