First of all Absinthe is generally a very strong alcohol (upwards of 190 proof) so that in its self will have an effect. But it is also believed to have a further effect due to the addition of various herbs, these herbs contribute to the intoxicating effect. The effects on every individual is subjective, most describe a sense of clarity or lucidity. It is a misconception that Absinthe will make you hallucinate or go mad. But that said it is a much different experience than drinking beer. One will only need one or two glasses to feel its effects, any more and you will just get dangerously drunk