“Trap Spread Choke” is not a phase to type into google image search. Below are some fancy “borrowed” photos illustrating many fine prepress principles of trapping including spreads and choke. I googled these terms so you wouldn’t have to. Donations are gratefully accepted via PayPal.
CMYK Printing
Spot Color to CMYK
Overprinting
Trapping, Chokes & Spreads
Density Reduction
Trap Edges in InDesign
InDesign is not a preflighting tool. That said, some introductory videos are available here: http://tinyurl.com/InDPreflight1
A typographic, designological, visulicious extravaganza!