Allosexual means you do feel sexual attraction. If you look at a person and you believe they are sexually attractive, you are allosexual.
Asexual means you do not feel sexual attraction. If you do not think anyone is sexually attractive, you are asexual.
Asexuals can have romantic relationships. Plently of asexuals want relationships, just no sex.
Some asexuals are aroace, or aromantic and asexual, meaning they do not feel romantic attraction or sexual attraction.