What is GNU Info for?

I understand what GNU Info is and how to use it, but what is it for? Why does it exist in parallel to the man pages? Why not write detailed man pages rather than provide a separate utility?

sed on OSX insert at a certain line

So I’ve been using ‘sed’ on linux for a while, but have had a bit of difficulty trying to use it on OSX since ‘POSIX sed’ and ‘GNU sed’ have so many little differences. Currently I’m struggling with how to insert a line of text after a certain line number. (in this case, line 4)

What are the differences between bsdtar and GNU tar?

I’ve always used GNU tar. However, all GNU/Linux distributions that I’ve seen ship bsdtar in their repositories. I’ve even seen it installed by default in some, IIRC. I know for sure that Arch GNU/Linux requires it as a part of basedevel (maybe base, but I’m not sure), as I’ve seen it in PKGBUILDs.