I am interested in buying a wireless keyboard and mouse.

Digital probably refers to the wireless technology used to connect the mouse/keyboard and the computer.  The two common standards of wireless are RF and Bluetooth, both of which are basically types of radio technologies.

Keyboards and mice do not have to be complex articles.  You can get them with extra "feature" buttons, e.g. to launch an internet browser or a media player, but more often than not these are largely superfluous to requirements of business.  Prices vary vastly between about €30 for a basic Logitech model to circa €240 for the bells-and-whistles Microsoft model.

The €200 difference does get you, for example, a laser rather than ordinary optical mouse, Bluetooth rather than RF wireless and a 4-way rather than 2-way scroll wheel and a built in USB hub.   The Microsoft model is most likely cooler too - it does come with a backlight- but one must weigh such features against cost effectiveness and ask the business reason fot it.  On a maintenence front, the Microsoft model only needs to plug one thing - the receiver - into the PC.  The logitech model has three cables coming out of the receiver - one for the power, one for the keyboard and one for the mouse - a functional but clunky solution.

The more expensive keyboards appear to be aimed mostly at the home and entertainment market, e.g. computer gamers with too much money.  When Dell ship a keyboard, as standard they send a slimline, quiet, comfortable keyboard with only the standard functions and taking up minimal table real estate.  These work perfectly well and should act as a guide when looking for a wireless keyboard.  Once your keyboard price goes above the €50-€80 mark, you are going to get less business value for money.
Mouse and Keyboard Purchase Tips

  1. Look for keyboards which are not too loud, are comfortable to use and are devoid of fripperies
  2. Read customer reviews online - Amazon.co.uk and Komplett.ie are great for customer reviews, which are good for getting a feel for the things that "features" lists can't tell you.
  3. Choose a manufacturer who has a good reputation, e.g. Logitech.  Again, customer reviews are a great boon here.
  4. Do not be suduced by extra buttons either on the mouse or the keyboard: you may never use them.
  5. Think hard before spending more than €50-€80.