Conscious sedation is an anesthetic technique that aims to produce a state of relaxation in the patient, favouring pain control. With this type of sedation the patient remains conscious, breathes autonomously and she/he is able to respond adequately to physical stimula and verbal commands.
It is also important to point out that conscious sedation avoids general anesthesia with all the contraindications that it entails and it also causes the patient to have an anxiolytic (as well as analgesic) action that allows the treatment of teeth that would otherwise have to be extracted.
An interesting article that appeared in the British Dental Journal reports a study done on 118 patients treated with conscious sedation over a period of two years. The results are astonishing: with this technique 105 total anesthesia were avoided and 141 teeth were restored rather than extracted (source: Odontoiatria33).