Posts format

Hi!
I don’t know why but when I wrtite a article the format is not normal, is like this:
<span> (my text) <span>

and when I use a image it doesn’s show the image, but something like:

[caption id="attachment_19" align="alignnone" width="535"]<a href="http://www.site.com/wp-content/uploads/2013/05/nameofimage.jpg"><img class="size-full wp-image-19" alt="nameofimage" src="http://www.site.com/wp-content/uploads/2013/05/nameofimage.jpg" width="500" height="300" /></a>dd /caption]

How can I make it normal, can you tell me please?