On a normal "Cartesian" machine, each actuator ( a motor and a linear rail, named alpha, beta, gamma ) corresponds to an axis ( like X, Y and Z ).
But on other machines, the position in cartesian space ( X, Y, Z ), must be converted, using math, into a more complex position for the actuators.
This is the case for example of linear delta ( often just called "delta" ) machines.
Currently smoothieware supports the following arm/motion solutions :
To configure your machine for the right type, see it's specific page.