How to get the value of checkbox?

How to get the value of checkbox?


How to get the checkbox is checked or unchecked in alert?

I selecting checkbox alert shows 

::::selected::::::+ Checked 

In above output line  Checked is the value of checkbox i s checked or unchecked  
My code:
   <span>Show checkbox
   <input type="checkbox" name = "actChk" class = "actChk"  style="margin-left: 10px;"></span>
   <input type = "button" id = "submits">submit</button>
$('# submits ').click(function(){

alert($('input:checkbox[name=activitiesChkbox]').val() )
});