There are many different types of keyboards that are available. Rubber domes, buckling-springs, scissor-switches, mechanical switches, and more are out there for your choosing. However, they all have one thing in common. Every keyboard out there is digital, and one company is looking to change that.
When I say that keyboards are digital, you might be a little confused. Basically, there are two different types of input that a computer can receive: digital and analog. Digital devices transmit in binary. Every signal is either a 1 or a 0. Either you're pressing a key, or you're not pressing it. Pretty simple stuff.
Analog inputs can send a variable signal, which changes depending on how far or hard something is pressed. Think of the analog sticks on your Xbox or PlayStation controller. They're called that, because they transmit an analog signal, which changes based on how far in any direction you move it. Now imagine that sort of sensitivity on a keyboard switch. It would work something like the graphic below.
As the key is pressed, the signal transmitted changes. This is useful in games when you want to move one direction or another, but you want to have some control over the speed that you do so. If you want to slowly move forward, you might gently press the 'W' key, just the same as you would lightly nudge the stick on your controller forward.
A company by the name of Wooting is planning to release a keyboard that is completely analog. While we don't have a lot of information about the Wooting One, aside from the sweet analog input, we do know that it will be fully RGB backlit, and will be tenkeyless (meaning that it won't have a numberpad). It should be out sometime later this year.