is an adverb, meaning 1. approximately. It is commonly used to indicate time:
Ex. It is about ten o' clock
2. Very Close to:
This is about the best we can hope for.
3 (especially British English) In many directions; here and there.
The children were rushing about in the garden.Around
is an adverb too, meaning 1 Approximately, very similar to about in this sense
He arrived around five o'clock.
2 on every side; surrounding somebody/something (differ from about this sense)
a yard with a fence all around.
3 (especially North American English) (British English usually round) moving in a circle
How do you make the wheels go around? (very common meaning of this word)
4 in or to many places
We were all running around trying to get ready in time.
This is our new office—Kay will show you around.By
is a preposition meaning 1 near somebody/something; at the side of somebody/something; beside somebody/somethinga house by the river
The telephone is by the window.
Come and sit by me.
2 used, usually after a passive verb, to show who or what does, creates or causes something
He was knocked down by a bus.
3 used for showing how or in what way something is done
The house is heated by gas.source Oxford Dictionary
Dicas de material.
Grammar in Use
Grammar in Stepshttp://www.englishpage.comhttps://www.englishexperts.com.br/forum/about-x-around-qual-a-diferenca-t22199.htmlhttps://www.englishexperts.com.br/forum/uso-do-by-t2644.html