Previously.. Facebook was offering buttons like..
1) Confirm 2) Not now
The Not now button was useful as if you chose not to be friend and click not now button. The notification for that friend request will be hidden. But you'll be still able to see it if you check it manually by clicking on FRIEND REQUESTS.
For the person who sent you the request..It'll be showing as pending request.
Now a Days.. When someone send you a friend request. 2 buttons appears
1) Confirm 2) Delete
If you chose to DELETE REQUEST. What happens is... There's 2 options..
1) Only Delete The Request
2) Delete + Mark The Request As Spam
1)Only Delete The Request :
In this option.. The request sender will not be able to send you request for some fix amount of time(I Don't Know exactly Maybe 8-12 Months)
2)Delete + Mark The Request As Spam
In this option.. The request sender will not be able to send you request forever!Same like blocked from sending you request again.
In both the cases.. The Sender will notify that you deleted his/her request as there'll be no option for friend request...only for message depending on your privacy settings.
Did someone deleted your request marking it as spam?Wanna send friend request again?Read my another post here..