Can I ask about technology? Sometime I have some doubts about hardware issues, for instance, what is the difference between LCD Monitor and LED Monitor. Can I ask this on ServerFault or there is another Exchange community with this purpose? Sometime ago I had to do a hard research about it, Because many sources says that there is a new technology but, finally, It was the same technology of LCD with a different backlight

It depends on what the hardware is and what it's being used for. Your example LCD vs LED Monitors would not be suitable for Server Fault, as it doesn't appear to have anything to do with Server, Network, or related equipment. It seems like an End User type question, which is suitable for Super User.

Also, most people should have doubts about convoluted marketing terminology. Today's "LED Monitors" are LCD Monitors with LED Backlighting (LCD Screens used to use cold cathode backlighting). There are many more LEDs and they do not burn out as easily, so it's a mildly superior technology, but it's still an LCD Screen. They use the term "LED Monitor" to confuse buyers, as there are also OLED screens (used in some cell phones, and various other smaller screens), where there is no LCD or backlighting, they only use LEDs.