Dear CNC admin & all!

Not long ago our company decided to purchase some spindles with collet. We need gripping collets as well as feed ones. But mostly spindles itself. But how I would choose the right one?
Being completely newbie, I'm trying to find articles for-to understand all about spindles and various equipment for metal cutting for different materials? E.g., which spindles I need for milling cutter? May be spindles differs by sizes or alloy they made of? How I can find articles about this? Some special sites for such newbie like me?

Glad to see any links or advice

Thank you in advance
Hirondelle