It's a bit difficult to explain, but they are different. The [ right ][ /right ] tags "float" block elements to the right, but it also aligns text to the right in that block element. [ text-right ][ /text-right ] only aligns the text to the right. [ right ][ /right ] will "float" your images to the right, allowing text to wrap around it,
much like this.
One can only really know the difference if they play around with it.