I've designed a custom calculator for any client. Now he really wants to integrate it right into a wordpress site and requires help. The calculator is pure HTML+CSS+JS with no PHP code.

He wants the calculator to look included in the page's primary content (not within the sidebar). What's this regarded as in wordpress, a wordpress plugin? a widget? How can i learn more about integrating such tools in wordpress?

P.S. He wants the calculator to look inside a page at http://site.com/services/calc/ and also the page has other content aside from the calculator.

The simpleOruntidy way is always to just drop it as being a code snippet right into a page. See: http://codex.wordpress.org/Using_Javascript#Javascript_in_Posts

The greater difficult but ultimately more multiple-use way is always to build this like a wordpress plugin, known as using a shortcode like [calc]. See: http://codex.wordpress.org/Writing_a_Plugin

Hope this can help!