checkinstall is a utility that you use to create a slackware package ...
so your source compilation goes like this (generic)
./configure
make
make install
and with checkinstall you would do
./configure
make
checkinstall
you will be prompted for several options, and then checkinstall will create a slackware package(tgz) and install that package.
With source code, to uninstall, you need to count on a "make uninstall" rule in the makefile
With checkinstall however, you do removepkg whatever the title of your package.
and yes, if you want to get rid of a program, removepkg program is easier than searching for all the files you can remove... so in that way it makes life easier
even better would be to see for yourself
http://asic-linux.com.mx/~izto/checkinstall/index.php