If something doesn't matter, it's not important. Take a look at some examples of this:
It doesn't matter to me where we have dinner. (The restaurant isn't important to me.)
It doesn't matter what happens, I'll always love you. (What happens isn't important, because I will love you in any case.)
On the other hand, if something matters, it's important. A couple of examples:
What you do matters more than what you say. (Your actions are more important than your words.)
Being on time really matters. (Being punctual is important)
Note: If we put "to you" or "to Mary" afterwards, it means that the thing is important or unimportant to the person in specific. If not, then we're speaking more in general. For example:
Clothes really matter to Barbara. (Clothes are important to her personally.)
Does Facebook matter? (Is Facebook important in general?)
Here's the question form:
Does the royal wedding matter?
Does it matter whether we meet at my place or yours?
Matter is regular in its form, and you can use it in all verb tenses.
People often talk about "what matters," and this refers to what's important to them. For example: what matters to me is how I spend my time.
What matters to you?