I consider Brett's answer incomplete and rather subjective, so I'll toss in my two cents.
First, there are great differences between the different switch types - and some of them can be rather annoying to the wrong person! It all boils down to preference.
I will explain in short:
1. Linear and Tactile
- Linear switches travel smoothly right down to the bottom. There is no feedback to your finger when the actuation happens so unless you are confident about the key travel/bottom-out (or look at your screen) you cannot be certain that the key has been actuated.
- When you push down a tactile switch, you can feel the actuation for when it happens the switch will give in a bit. In other words, the peak actuation force required for activation is a bit higher and upon activation it drops.
Out of these, I prefer linear for typing and tactile when gaming.
2. Clicky and Silent (applies only to tactile switches)
The names are pretty self-explanatory. I recommend watching a couple of videos in order to gather an idea about how clicky switches sound. Many people are very annoyed with the sound while others love it. Be very careful when you pick this for your girlfriend as it can turn out to be an annoyance either for you or for her...or both of you might actually enjoy it! ;)
I used to like clicky switches back in the day but I've grown to admire the soft bottom-out sound only.
3. Actuation force
Different switches have different springs in them - some are lighter, while some are heavier. This is again a very important factor because some people tend to rest their fingers on the keyboard and are likely to accidentally actuate them.
I like heavier keys (60-70 grams peak actuation force) but most people tend to like 45g springs.
4. Switch travel
- Classic Cherry switches have a 2mm travel before actuation, out of a total of 4mm travel.
- The new Cherry switches, Silver use the lighter (45g) springs and are a linear switch with a shorter travel time (1.2mm actuation, 3.4mm total travel distance).
Kailh switches are basically a Cherry MX rebrand after their trademark expired. There are also other brands which copy Cherry but let us not digress that far.
Now that you know all this, here is a listing of the most common Cherry MX switches:
(switch colour - tactility, noise, stiffness, travel)
- Red - Linear, Silent, Soft (45g), Normal (2/4mm)
- Silver - Linear, Silent, Soft (45g), Short (1.2/3.4mm)
- Brown - Tactile, Silent, Soft (45g), Normal (2/4mm)
- Blue - Tactile, Clicky, Soft (50g), Normal (2/4mm)
- Black - Linear, Silent, Stiff (60g), Normal (2/4mm)
- Green - Tactile, Clicky (loud), Stiff (80g), Normal (2/4mm)
- Clear - Tactile, Silent, Stiff (65g), Normal (2/4mm)
- Grey (dark) - Linear, Silent, Stiff (80g), Normal (2/4mm)
- Grey (light) - Tactile, Silent, Stiff (80g), Normal (2/4mm)
- White - Tactile, Clicky (soft), Stiff (80g), Normal (2/4mm)
As for a keyboard recommendation, there are also different formats - depending on the use case, you might not need a numpad. I will recommend in each:
Ducky Shine 5 RGB, because
Sturdy and overall flawless build quality, which is very characteristic for the Ducky brand. Those keyboards are held in high regard even in the keyboard enthusiast circles;
You can pick between Cherry MX Brown, Red, or Black switches;
14 pre-programmed lightning modes, along with 2 fully customizable (per-key brightness, colour, and pulsation);
ABS Double-shot keycaps. ABS is a high quality plastic (usually last for well over 15 years before losing its characteristics) and only very rarely do you find stock PBT caps, with PBT being considered by many the ultimate plastic allow to last nearly forever on a keyboard;
All the macro and settings profiles are stored on the built-in memory, meaning you can move it wherever and still keep your settings;
USB cable is detachable and replaceable. You can buy another, fancier one, or make your own if you so desire!
What the keyboard lacks for some people are dedicated multimedia/additional buttons, however all that either built-in (Fn+key combo) or is fully customizable anyway.
Ducky One RGB TKL, because
It sports a smaller size and is a more compact fit on your desk, leaving more space for your mouse and providing a more comfortable stance with less spread hands;
Again a very solid build quality;
Slim bezels and compact frame which further enhance the space-saving benefit of TKL keyboards;
Detachable and replaceable cable allows for better portability;
Again ABS doubleshot keycaps with sandblasted finishing;
Cherry MX Blue, Red or Brown switches;
10 lighting presets with three custom lighting zones;
Evenly lit legends on the keycaps.