Graham bemethavinci Bootstrap is just a set of CSS classes and a bit of javascript for the more fancy stuff
it uses media queries to test for small screen widths
https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queries/Using_media_queries
I guess there are other similar templates Bootstrap is just the most widely used
No matter what it would entail a complete re write of your site to implement a different template as none of the classes or structure would match