"You may not actually need root permissions to install a given software package, or you may not have access to root privileges via sudo or su or other methods.
One of the ./configure script's common options is --prefix, which changes the base installation directory from whatever the default is. So on a system where I have no root privs at all, I can still install this software to my own home directory:
./configure --prefix=$HOME make make install
The ./configure script has lots of other options, some common to all, some dependent on the particular package you're compiling. Use ./configure --help to see them all."