Like some of the other mouses in Microsoft's collection, the Explorer Mini uses the compant's proprietary Bluetrack technology.

It works on more surfaces than both optical and laser mice, virtually anywhere including granite countertops and carpets. The only two exceptions seem to be clear glass and mirrored surfaces.  The sensor really is better than one using laser, but you really have to try it on surfaces like marble to really appreciate it.

Having Bluetrack on the portable version is even better than having it on the normal Explorer Mouse.  That's because the Mini is more likely to be paired up with a laptop, so it's good to know that you can use it on just about any surface you come across while travelling. 

As well as its all-terrain properties, the Explorer Mini is a great mouse in its own right.  The gentle curves make it comfortable, and it feels natural when you hold it in your hand.  There are two thumb buttons on the side.  Too many laptops only have one, and some have none.

One important detail is that the Explorer Mouse comes with a charging station, which isn't the case with the Mini.