Slackware is one of the earliest Linux distributions and actually it is the oldest still being maintained. It is also the only one that keeps all packages vanilla flavor, which means, none of them are tweaked in any way.
From the Kernel to the last piece of software it is packaged just like the developers made it, with no distribution customization.
Slackware has been told to be difficult to maintain, and to work with, it has also been said that it has no package manager tool.
To say the truth I was afraid of the same things the first time I installed Slackware on my old Lenovo T60, but I’ve got a big surprise.