What is a knitting machine? – in short
The “modern” vintage knitting on a knitting machine is kind of like weaving on a loom in that you are making a fabric row by row with mechanical assistance, except latch-hooks make a knit stitch by pulling in and out when you crank a carriage across. A knitting machine may be electronic, but most are not. Most knitting machines are a purely mechanical tool, albeit one with a lot of moving parts. More on the basics of knitting machines from a guild in the UK.
What is a knitting machine? Pt. 2 – this time with a dash of history!
I’ll refer you to a longer post I wrote about the history of knitting machines (lots of links to external resources).
Is knitting by machine cheating if you already know how to hand-knit?
I consider it a whole separate art form. Hairpin lace and broomstick lace are not cheating versions of crochet just because they incorporate a specialized tool. Weaving on a loom is not a cheating way to make fabric either. A knitting machine is just another tool to make fabric that takes a very rarefied skill set which takes time, patience, and practice to learn just like any other art or craft. It may make a knitted fabric faster that knitting by hand, but it also has limitations that hand-knitting does not have. I still hand knit all the time. It is easier (for me) to hand knit, more portable, and in many ways more versatile.
HOWEVER, if you take up machine knitting, you should NEVER pass off machine-knitted work as hand-knitted. This unfairly devalues handknitting which takes much more labor and time. We may call our machine knitted objects “handcrafted”, “hand made”, “home made” or “created by”, but never “hand knit”.
Where can I get the instruction manual for x knitting machine?
Tons of free knitting machine manuals can be found in PDF form on these sites: http://machineknittingetc.com/ and Mostly Knitting Machines. There are also great resources on YouTube.
My own posts or pages about specific knitting machines that have passed through my hands:
Bond Ultimate Sweater Machine
KnitKing PC Bulky/Brother KH 260
Unravelling Argyle 
Good day
I am looking for a ribmaster for the knimaster 4500 knitting machine.
Kind regards
Cobie