As I get back into traveling more internationally, Global Entry is on my list as well. I've been through my share of passport control lines, some moving quickly, others taking hours. Anything that cuts the time in lines is good.
So what is the Global Entry program? This is a program that gives expedited clearance to travelers coming into the United States. Using automated Global Entry kiosks at select airports, program participants present their machine-readable passport or US permanent resident card, place their fingertips on the scanner for fingerprint verification and complete a customs declaration. The kiosk issues a transaction receipt. The traveler is directed to baggage claim and the exit. The program is intended to speed up passport control.
If you have not applied for either program and you travel internationally, apply for Global Entry as it makes you TSA Pre-check eligible and it is only $15 more. TSA Pre-check does not make you eligible for Global Entry. Keep in mind both programs have non-refundable application fees ($85 for TSA Pre-check, $100 for Global Entry) whether you are accepted or not. Each traveler must apply separately and be approved to participate in either program.
For complete program details and eligibility go to https://www.tsa.gov/tsa-precheck and http://www.cbp.gov/global-entry/about