These two parts of speech have greater impact connecting phrases or sentences. Since everyone can easily identify other part of speech and these are the areas which confuse us from its usage. I have learned to be more specific and accurate to use them properly. Still, knowing all part of speech are interesting and it boost more confidence to speak well in any forms of occasion.
F.AN.B.O.Y. S for Conjunction
In, on at and etc. for Preposition.
Conjunction and preposition are precise due to words it shows however their usage is redundant and in demand.