How does airport security find forbidden items in suit cases?

They have Scanners, that work like xray machines and sonograms. A suitcases material might not block out some of the methods and they basically see an xray image of the contents inside, some materials glow, such as liquids, whuch they will ask you to pull out and possibly measure and identify the contents, for example I was stopped like 2 years ago when flying from texas to Colorado and they asked me to empty my bag they scanned and pulled out a pickle in a bag, the pickle wasn't the issue, just the liquid juice, told me to pour it out since it was exceeding the allowable quantity. Then they have metal detectors that identify electronics, weapons and so on. When they see it, they will tear apart your luggage to take away what is allowable and not. Some exemptions may apply since I was in military they allowed me to transport weapons, gear, bullet proof vests and so on.