Linux Source command use cases versus bash shell script | use cases for linux source command

This video talks about source command in Unix/Linux and explains.
the difference between source command and bash shell script.

BUCKET_NAME=redish-colman
PRIME-URL=das/amzon/mumbai/

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echo $BUCKET_NAME

"Mahesh's Birth day : today
cal -3
echo "happy birthday Mahesh"

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BUCKET_NAME=redish-colman
PRIME-URL=das/amzon/mumbai/

echo $BUCKET_NAME