An "ideal beauty" is an entity which is admired, or possesses features widely attributed to beauty in a particular culture, for perfection.
Ugliness is considered to be the opposite of beauty.
The experience of "beauty" often involves an interpretation of some entity as being in balance and harmony with nature, which may lead to feelings of attraction and emotional well-being. Because this can be a subjective experience, it is often said that "beauty is in the eye of the beholder."
There is evidence that perceptions of beauty are evolutionary determined, that things, aspects of people and landscapes considered beautiful are typically found in situations likely to give enhanced survival of the perceiving human's genes.