It is the lack of romantic attraction and little to know interest or desire in forming romantic relationships with people of any gender. 

Aromanticism is a valid romantic orientation and may involve other forms of attraction which are not romantic (e.g. platonic attraction).

Aromantic people, known as “Aro” or “Aros” people experience little-to-no romantic attraction, which does not mean that they do not experience love in other forms (outside of romance).

While there have been no comprehensive studies about the frequency of aromanticism globally, you can read the ARO CENSUS REPORT by AUREA which highlights the makeup of the aromantic communities in the countries surveyed in the study.