I suppose that it is not rare that tying for a solution the approach will be installing packages on the Raspberry PI environment, check how the stuff works then abandoning the solution to move to a different approach. This usually means sudo apt-get install a certain number of packages and the related dependencies occupying storage space.
Deciding that a certain approach is not what we want we can remove the packages in the same way se installed them:
$> sudo apt-get remove <package name>
Then in few times it may occur that we go low of storage space, especially when using only a 4 or 8 Gb microSD storage. As a matter of fact all the downloaded packages are cached by the linux operating system and these are not physically removed from the system when we simply remove the package. So, when we are sure that a set of packages are not needed it is a best practice to use a couple of apt-get features to really clean the system:
$>sudo apt-get autoremove
All cached packages and their dependencies are removed from the system definitely freeing lot of space. This command does not affect the components that are instead in use. As there are also cases where some other stuff (this maybe also consistent) downloaded by the update / upgrade keep files no more needed to the system. In many cases during an upgrade there are packages and components replaced by the newer one downloaded while the old are retained. Maybe that the system needs a rollout to the previous version, the user needs to save them for some reason and so on.
To definitely clean the system you can also launch the cleaning command
$>sudo apt-get autoclean
to remove all the unused packages from the system. You can check the available storage space in all the linux partitions with the command df (disk-free) generating a result similar to the example below.
pi@RPImaster ~ $ df
Filesystem 1K-blocks Used Available Use% Mounted on
rootfs 919001196 4502680 867792852 1% /
/dev/root 919001196 4502680 867792852 1% /
devtmpfs 437856 0 437856 0% /dev
tmpfs 88432 292 88140 1% /run
tmpfs 5120 0 5120 0% /run/lock
tmpfs 176860 0 176860 0% /run/shm
/dev/mmcblk0p5 60479 14537 45943 25% /boot
/dev/mmcblk0p3 27633 442 24898 2% /media/SETTINGS_