What are Prepositions
Prepositions are those words, which show the relationship of Nouns (or Pronouns) with the other words in the sentence. Prepositions are used before Nouns (or Pronouns) in the sentence.
About describes the Nouns or Pronouns and it is used when making estimates about the quantities of nouns and pronouns.
He told me about his journey.
The train will depart in about ten minutes.
I was thinking about you last night.
The weight of the bag is about 15 kg.
This article is about prepositions.