what is "debugging symbols" and "debug binaries"

[jinson2k]

in setup process，（See the picture）
"Download debugging symbols"
"Download debug binaries（requir es VS 2015 or later）"

1、what is "debugging symbols"? what's it use for ?
2、what is "debug binaries"? what's it use for ? and is it just use in VS2015 or later)