jquery on the difference between the occurrence of callback events and the occurrence of parallel events

No callback:

<! DOCTYPE Html>"Utf-8"><script src="Http://cdn.static.runoob.com/libs/jquery/1.10.2/jquery.min.js"></script><script>$ (document). Ready (function () {$ ("Button"). Click (function () {$ ("P"). Hide ( +); Alert ("now the paragraph is hidden.");//Events side by side, the order of occurrence is not clear}) ;</script>
With callback:
<! DOCTYPE Html>"Utf-8"><script src="Http://cdn.static.runoob.com/libs/jquery/1.10.2/jquery.min.js"></script><script>$ (document). Ready (function () {$ ("Button"). Click (function () {$ ("P"). Hide ("Slow", function () {alert ("the paragraph is now hidden.");//first hidden after the window, there is a definite relationship}); });});</script>
jquery on the difference between the occurrence of callback events and the occurrence of parallel events