Unfortunately, no. It means that you are eligible to get in line to apply for one. Depending on the category, the wait ranges from two or three years to well over twenty years - and by the time you qualify, the time may well have increased considerably. Sometimes, the backlogs double or triple with very short notice. A few employment-based categories are "current" meaning that you can indeed get a Green Card immediately as soon as the paperwork is completed (the paperwork itself can take several years, though).