So, how do court stenographers copy down testimony so quickly? They pretty much type entire syllables all at once (often more than one syllable!) and use lots of abbreviations.
For example, on a standard keyboard, you type one or two keys at a time. If you wanted to spell "tar", you would hit T-A-R in that order. But on a stenography machine, you hit all three keys and release them at once to type the entire syllable in one fell swoop. If you try that at your computer right now, there's no guarantee that the letters would spell "tar". It could come out as "art" or "rat" or "tra". But, a steno keyboard only has a little more than 20 keys, as shown in the diagram above. There's also a "number key" which works like a shift bar, and is used to type numbers with the other keys.
There are seven consonants, followed by four vowels and an asterisk, and then ten more consonants at the end. For "tar", you would hit the T on the left, the A, and the R on the right, then release all at once, at which point the paper scrolls to allow the next line to be used. Many letters are absent from this sequence of keys, and are instead substituted with combinations of letters. For instance, a the word "lick" would be written "HREUBG". These combinations are arranged strategically, so that most sequences of consecutive consonants in English words are ordered correctly when typed.
There's much more to the stenography machine and its "secret code" than can fit here. If you'd like to learn more, you can download the book Stenotypy from Google Books.
