The pasuk says וירח ה' את ריח הניחוח - Hashem smelled the pleasant fragrance of Noach's korban. The medrash expounds that the "smelling" connotes a viewing of the future. Hashem smelled the smell of Avraham Avinu who came out of the burning furnace, the smell of Chananya Mishael and Azarya coming out of the burning furnace etc. the smell of the generation of shmad [religious persecution] etc. meaning that Hashem saw all of these events and in their merit he made a covenant that there will never be another mabul.
The moon is called ירח which contains the same letters as ריח, because in the future the moon will be healed from its blemish, just like the Jewish people that will in the future be healed from there blemishes - שהם עתידים להתחדש כמותה even though now they are not in a good state, Hashem smells their future purity and therefore even now we create a fragrant aroma before Hashem. That is what the gemara in Eiruvin [21a] means when it says that even the reshaim will give a good smell in the future which can even be perceived now by Hashem. [Shem Mishmuel]
Now that we understand that "smell" relates to the future, we can understand what we accomplish om Motzaei Shabbos. Shabbos encompasses all of time - past, present and future [שפת אמת תר"ן ד"ה בפסוק, מאור עינים ליקוטים ד"ה שבת, פרי צדיק ויחי אות ז]. On Motzaei Shabbos we return to the world of the present. In order to give us the strength to get through the sometimes difficult times that we will face, we make havdala which symbolizes past, present and future. We make a בורא פרי הגפן and the word בורא refers to the past [Brachos 52b]. We make a בורא מאורי האש on the fire and we know that the fire is renewed every second. That symbolizes the present. We also make a bracha on the bsamim, a bracha on the ריח which as we saw, symbolizes the future.
The Zohar says that the whole world stands in the merit of ריח. This can mean that we have the strength to keep going knowing what will happen in the future and that we will be redeemed. [See Pachad Yitzchak Yom Kippur Maamar 6!]
Tolna Rebbe Melava Malka Parshas Noach 5761