je ne sais quoi is a French expression that literally means "I do not know what", in the Portuguese language.
Even though it is a French expression, "je ne sais quoi" is used almost all over the world when someone wants to explain something that is inexplicable, that is, when something or something attracts attention, it stands out, but no one knows exactly what é.
The "je ne sais quoi" is commonly related to a "what" or something "more" that is positive in an individual's personality, physical characteristic, or makeup, but which is not easily identifiable. It is something that someone considers special about someone else, but cannot say for sure what it is.
Examples: "The new student has a certain je ne sais quoi" or "My neighbor is very ugly, but he has a je ne sais quoi that attracts me".
Normally, a "je ne sais quoi" is not necessarily a person's physical appearance, such as eye color, smile or body definition, but rather a personality characteristic, the way he talks, how he walks, how he reacts to certain situations, among other actions that particularly please or delight certain person.
In general, the "je ne sais quoi" can be used to express someone who is charming or sensual, but without specifying which factor arouses these feelings in the interlocutor.