Nick,

Let me try to answer your questions

1 - Word
2 - Very simply, if Drive is a positive value, you move forwards, and vice versa
The pwm magnitude can be set by the ABS(Drive) value
3 - The LOOKUP command is checking if the value in Drive is positive or negative and filling Direction with either f or r.
Understandably, the board wants the direction input to it as either 'f' or 'r' for forward or reverse

Regards