Halal mean permissible in Islam and Tayyiban means wholesome: healthy, safe,nutritious, quality. There are certain foods like pork, blood, intoxicants and alcohol that are prohibited for consumption because the detrimental effects to health. Wiki
Why does Halal matter?
Halal matters pertaining to food is to make sure we eat only safe healthy food. This is one of the tenets in Islam because only a healthy body can one put together strong mind and soul.