Technical describes a specific art or science, or training for a particular job. If you have trouble with your new computer, you might call for technical support, but a technical school teaches you a certain craft, like how to weld.
Technical comes from the Greek tekhno, which means "art or skill." Anything technical requires both art and skill. If you're an Olympic gymnast, you have technical abilities. You might go to a technical school to learn how to be a chef, a mechanic, or a massage therapist. While being technical can be a positive trait, you don't want to overwhelm someone with technicalities. For example: If you're trying to explain how a car works to a kid and you start talking about manifolds, you're getting too technical.