"Advise" vs. "advice"

Advise is a verb, so it is used to indicate an action. So for instance:

I advise you to do xyz.

Advice is a noun that derives from advise. So you would use it as the subject or the object of your sentence.

• My advice is to do xyz.
• The best advice I can give you is to do xyz.

When you advise someone you are giving them advice.

More specifically, advice is a noun, that is, it is the thing that is being told to the person being advised.

Advise is the verb, or action, of giving someone advice.

Advice is the actual content or helpful tip or whatever it was you gave the person:

Their advice was helpful.

I need some advice!

Advise is the action of helping someone:

They advised me on writing a letter.

Someone advise me!