I prefer to have 3 partitions by default when I’m installing Linux. It’s usually a good idea to prepare the hard drives, partition it before hand when installing your operating system. I prefer to have /boot, / (root) and /home in separate partitions.
I have /boot so I can ensure that my system will boot at least into a console if I needed to make some maintenance jobs to grub or to /etc/fstab. With /boot I have some way of editing the system files.
Of course / is where the operating system files are.
I have /home to protect my files and to ensure I can make backups. If you need to jump from a distro to another one, all that you have to do is install it on / and then mount the existing /home to your installation. A lot of new users are asking how to install a distro without wiping out their data. Keep your data on a separate partition and your /home (user data) becomes portable.
Some other partition schemes are available according to one’s needs and use cases. Some would like to have /var/log on a separate partition for their servers. If you need to have a particular directory to have unique permissions and to not permit executable perhaps you should consider putting them in a separate partition.