Element

An element in the Document Object Model (DOM) has attributes, text and children. It provides methods to traverse the parent and children and to get access to its attributes. Due to a lot of flaws in DOM API specifications and implementations, those methods are no fun to use. jQuery provides a wrapper around those elements to help interacting with the DOM. But often enough you will be working directly with DOM elements, or see methods that (also) accept DOM elements as arguments.

Whenever you use jQuery's each-method, the context of your callback is set to a DOM element. That is also the case for event handlers.

Some properties of DOM elements are quite consistent among browsers. Consider this example of a simple on-blur-validation:

$(":text").blur(function() {
  if(!this.value) {
   alert("Please enter some text!");
  }
});

You could replace this.value with $(this).val() to access the value of the text input via jQuery, but in that case you don't gain anything.