As Elle said, most likely it is your battery or related.

Can the car be boosted using starter cables and another running car?

If you cannot boost it and it still does not do anything, check the
connections to the battery - clean them well. Get a battery terminal
cleaning tool from an automotive place and ask one of the people there
to show you how to use it, in case you don't know.
You may need to clean both cable ends so clean the wires with the
battery disconnected. One fat wire goes to the frame (that's your
ground). Make sure that wire makes a good connection on both ends and
the bolt that the terminal is sitting under is tight.

If the car can be boosted, your battery is most likely bad. You may
also need to check your charging circuitry (requires a multimeter - let
us know if you have one and know how to use it).
Sometimes if you tap a battery terminal lightly with a hammer, it comes
back to life. That is usually an indication that the battery has a bad
internal connection and should be replaced.

It could be other things as well (like your ignition switch, etc) but
it is a little early to tell. Let's hope it is just the battery.

Remco