Jquery mouseenter() vs mouseover()

You see the behavior when your target element contains child elements:

http://jsfiddle.net/ZCWvJ/7/

Each time your mouse enters or leaves a child element, mouseover is triggered, but not mouseenter.

$('#my_div').bind("mouseover mouseenter", function(e) {
  var el = $("#" + e.type);
  var n = +el.text();
  el.text(++n);
});

#my_div {
  padding: 0 20px 20px 0;
  background-color: #eee;
  margin-bottom: 10px;
  width: 90px;
  overflow: hidden;
}

#my_div>div {
  float: left;
  margin: 20px 0 0 20px;
  height: 25px;
  width: 25px;
  background-color: #aaa;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js"></script>

<div>MouseEnter: <span id="mouseenter">0</span></div>
<div>MouseOver: <span id="mouseover">0</span></div>

<div id="my_div">
  <div></div>
  <div></div>
  <div></div>
  <div></div>
</div>

Though they operate the same way, however, the mouseenter event only triggers when the mouse pointer enters the selected element. The mouseover event is triggered if a mouse pointer enters any child elements as well.

See the example code and demo at the bottom of the jquery documentation page:

http://api.jquery.com/mouseenter/

... mouseover fires when the pointer moves into the child element as well, while mouseenter fires only when the pointer moves into the bound element.