Euphoria means a feeling of great happiness and well being. In medical terms, it is recognized as the mental or emotional state which senses great elation. Euphoria is generally considered to be an exaggerated state, resulting from an abnormal psychological state, with or without the use of drugs, and not typically achieved during the normal course of human experience.
Euphoria is an effect. In general usage, you can experience euphoria when you get some prized possession or clear an important exam or get to meet someone special. Success and exciting events give us an exaggerated sense of happiness and this is normal. This wears off in time. In an abnormal case, the person feels euphoric without reason. In certain conditions like Hypoxia, when less oxygen is available for long periods, the first feeling the person gets is that of an unreasonable elation or euphoria. This is a condition that pilots are made aware of as they may have to undergo this in cases of certain emergency.
Euphoria for the present day generation may be a rock band. Our very own Indian rock band goes by this name. The reason is, perhaps, that they take their audiences to a state of great elation with their melodies.