From Using different delimiters in sed:
sed takes whatever follows the "s" as the separator
It is a good way to avoid escaping too much. Code is more readable if you use a delimiter that is not present in the string you want to handle.
For example let's say we want to replace lo/bye
from a string. With /
as delimiter it would be a little messy:
$ echo "hello/bye" | sed 's/lo\/bye/aa/g'
helaa
So if we define another separator it is more clear:
$ echo "hello/bye" | sed 's|lo/bye|aa|g'
helaa
$ echo "hello/bye" | sed 's,lo/bye,aa,g'
helaa