Advice, Practice, Licence etc. (those with c) are nouns and Advise, Practise, License etc. are verbs.

 Mnemonic:
One way of remembering this is that the word ‘noun’ comes before the word ‘verb’ in the dictionary; likewise ‘c’ comes before ‘s’, so the nouns are ‘practice,licence,advice’ and the verbs are ‘practise,license,advise’.