This article should help you to understand x3 common sink fitting industry lingo.
Options for sink fitting
“Top Mount” – this is for large or hard wearing sinks.
In this case the sink flange is set on top of the benchtop. This is the most cost effective option, and ideal for any situations that will see a lot of use and wear like rental properties.
“Under Mount” – this is by far the more popular option, as it is seamless and makes the sink less obtrusive, placing more emphasis on the benchtop itself.
The name means just what it suggests; namely, that the sink is mounted under the benchtop rather than on top of it. This makes wiping the bench off into the sink easier. Under this category you also have other options, like having a single drop bowel or having your top come up through the stone rather than from the sink.
“Flush Mount” – this is like a mid-way option between the first two.
In this case the sink flange is flush or level with the surface of your benchtop, making it good for wiping the benchtop into the sink like with the under mount.
An advantage that this option has is that it is resistant to chipping at the edge of the sink, unlike the under mount where the edge of the stone is exposed and vulnerable to heavy pots and the like.
One aesthetic aspect that people may not like about this type of mount is that there will be a sliver of silicone filling in between the sing and the stone (usually around 1 or 2 mm).
Also because your sink will be entirely visible, you need to think more carefully about the exact size and shape of your sink, unlike the under mount where the top part of the sink will be hidden.