noun
freebie; free gift; something extra
Commonly refers to a small extra item given free with a purchase, or more broadly anything added as a bonus.
この雑誌を買うと、おまけがついてくる。
If you buy this magazine, a free gift comes with it.
おまけに
On top of that, I got another present as a bonus.
noun, noun or participle which takes 'suru', intransitive verb
Used when a seller gives a discount or reduces the price, often as a favor or to make a sale. Can be used as a suru-verb (おまけする).
もう少しおまけしてもらえませんか？
Could you give me a little more discount?
あの店はいつもおまけしてくれる。
That shop always gives me a discount.
noun
embellishment; exaggeration; addition
Refers to adding extra details or exaggerating when telling a story; often used in the phrase おまけがつく.
彼の話にはいつもおまけがつく。
His stories always come with embellishments.