Digital Download

 I`m going buy the digital download today but what will happen wen i do it do i get papers that say i can install it again if i get a new pc or do i new to buy a new one?

I mean if i buy the digital download can i use it again if i get a new computer or i need to delete and reboot my hardware on the pc i got now.

sorry for taking you`r time away but i just need a answer.

Ps This game rule have played it at a friends house.