Malay: an (affix)

[zzzwor]

What is the usage of the affix "an" in Malay?
e.g bual bualan,what is the difference of the two word?

 

[entangledbank]

Basically it makes a noun from a verb:

beli "buy", belian "purchases, shopping"
makan "eat", makanan "food"
minum "drink (v.)", minuman "drink (n.)"
buat "make", buatan "product"

(I don't know the word bual, so I'm not sure if this is true for that.)