A small study of foreign language learning in adults compared two methods. One is known as the explicit or classroom method. This is the kind of traditional classroom teaching where students are taught a lot of information about grammar rules.
The other method is known as the implicit or immersion method. The idea here is to learn much the way children do when they learn a native language. That is, by being with native speakers and absorbing the language that surrounds them, generally without a lot of explanation.