It means each (cell) is specialized for a particular function, for example nerve cells receive and transmit nerve impulses while white blood cells can change shape and do their own function, these were 2 examples there are way more.
<em><u>Definitions of specialised. adjective. developed or designed for a special activity or function. synonyms: specialized specific. (sometimes followed by `to') applying to or characterized by or distinguishing something particular or special or unique.</u></em>
