Modelo: El novio es guapo. La novia es guapa.
So, In the abobve sentence, the adjective "guapo" is used to describe the novio (boy friend), and thus I will say that it is indicating that he is handsome.
So, The adjective "guapa" is used to describe the novia (girl friend), indicating that she is beautiful. In Spanish, adjectives need to agree in gender with the noun they modify.
So, "Guapo" is the masculine form, and "guapa" is the feminine form.
Therefore, when describing a male, you use the masculine form, and when describing a female, you use the feminine form.