A digital microscope can be achieved by integrating a camera into the microscope or by adding a digital microscope camera to a regular microscope.
An external digital microscope camera lends greater flexibility - you can use different cameras on the same microscope and vice versa.
Most digital microscopes and microscope cameras include basic image capture and documentation software.
Check to ensure the retailer can support the software - sometimes, post sale support is useful.
If you are not planning to do much high quality printing, you may not need higher resolution than 2.0 megapixel since most computer monitors are limited to 2 MP resolution.