@hm-us #9: The truss rod counteracts the tension of the strings. If you have an older acoustic guitar the neck may be stabilized by means of an unadjustable ebony inlay. Thze neck of any guitar must be built in such a way that it 'bends backwards'. The strings 'pull it straight'. An unstrung guitar will become unplayable after a while. If you string it, the strings will then touch some or all of the frets (no 'action' left).
Many acoustic guitars, especially Western and dreadnought style, use adjustable truss rods. There is some screw at one end of the neck. You need a flat blade screwdriver or an Allen wench to turn it, thereby increasing the backwards tension of the (steel) truss rod and forcing the strings closer to the fret board )or decreasing it, once the strings start to buzz). 'Tiny increments' refers to the turning of the screw. You can easily overdo it.
Most Spanish and concert guitars (with nylon or gut strings) are not adjustable. Still, they can be adjusted in a workshop. Most guitars with steel stings have an adjustable bridge (that's where the strings end on the body of the guitar) as well which allows you to adjust string length for exact intonation and string height for each string individually.
BTW, 'action' for keyboard instruments should be entered, too, by all means.
For guitars, however, 'Mechanik' refers to the mechanism used in the peghead (fur tuning). I's called 'tuners' (individual for each string) or 'machine' or 'tuning machine'.
See how 'action' is used in the following table which shows recommended string heights for various instruments:http://www.stewmac.com/freeinfo/Neck_relief,_...