At symbol bash

@ is considered a special variable in bash for expansion. $@ expands to all the positional arguments, starting from one.

Example

That is, for a given command:

./shop.sh apple banana

The arguments are:

• $0, "./shop.sh"
• $1, "apple"
• $2, "banana"

And $@ would expand to "apple banana".

See Special Parameters - Bash Reference Manual