Functionally, they are the same.
Float is CSS and can be applied to almost ANY element, including, but not
limited to <-p>, <table>, <img>, <h#>, etc.
Alignment is HTML, and can only be used in elements that accept the 'align'
attribute. The problem is that it means different things for different
elements, e.g.,
<div align="right"....
will right align the content of the div, while
<img align="right"...
will align the image itself to the right of the following content.
In distinction to the HTML align attribute, the CSS float is unambiguous in
its effect. It causes the element to be 'removed' from the flow of the
code, so that other adjacent code acts as if that element's code were not
there (although instead of ignoring it, it 'flows' around it, like a river
flows around an island).
The CSS 'float' style is the most useful style in the toolkit when it comes
to CSS layout. If you are interested in learning this method, get to know
float!
And read these -
http://meyerweb.com/eric/css/edge/index.html