Hello Friends,
The difference between undermount sinks and topmount sinks is in the installation process. Undermount sinks are installed to the bottom side of the countertop giving a clean edge on top. With an undermount sink, you will find that you can wipe crumbs off the countertop directly into the sink without encumbering the rim of the sink. While the topmount sink has a rim that sets on the countertop, making it easier to install.
Thanks and Regards
John marrison
Undermount Kitchen Sinks