Sounds where the airstream is obstructed, but not so much as to either stop it or create friction. Pronounce all or are very slowly and hear the difference between the vowel and the liquid consonants. Some languages trill r's, of course. In American English the r is considered a retroflex because of how the tongue flexes back toward the alveolar ridge (in most dialects). L is considered a lateral liquid because it is made by putting the tip of the tongue against the alveolar ridge, then letting the airstream flow around the sides of the tongue - laterally. In Welsh there is a really cool sound: an aspirated lateral liquid, basically l pronounced along with an "h" sound of air being blown over the sides of the tongue. (We'll talk more about aspiration, and nasalization and other neat words, later... :-)