In many parts of the English speaking world (UK, Ireland, Australia, Canada, and South Africa) “practice” is the noun, “practise” the verb. However, in the U.S.A the spelling “practice” is more often used for both the noun and the verb. Contrary to popular belief a significant minority of the American population also observe the distinction. If you are not sure about what a verb or noun is, it might be safer to just use the spelling "practice", as many Americans do!

The pronunciation is the same. In British English - also used in Ireland, Australia, NZ, S.Africa, and to a limited extent in Canada - the word 'practise' is a verb. For example, 'I'm practising' The noun is 'practice', as in 'I need some practice.' US English uses 'practice' for both the noun and the verb.

I think in Britain "practice" is a noun and "practise" is a verb. In the US, we use "practice" as both a noun and a verb.

practice = noun practise = verb