Advice significa consejos, o consejo.
A piece of advice es un consejo. He gave me a good piece of advice.
I am going to give him advice. Le voy a dar consejos. (O: Le voy a dar consejo.)
To advise es aconsejar, asesorar, advertir, informar: We must advise you of the dangers. I need you to advise me as to what to do. This is to advise you that our shop will close next Monday. He will advise you on this matter. My mother advised me against getting married.
I will advise you. Te aconsejaré.