To check disk space of Ubuntu 18 droplet with Digital ocean

Hello,
Could you, please, explain, in console of my Digital ocean droplet with Ubuntu 18
I run command to know how many of disk space I have

# df -HT
Filesystem Type Size Used Avail Use% Mounted on
udev devtmpfs 504M 0 504M 0% /dev
tmpfs tmpfs 104M 791k 103M 1% /run
/dev/vda1 ext4 26G 6.0G 20G 23% /
tmpfs tmpfs 517M 8.2k 517M 1% /dev/shm
tmpfs tmpfs 5.3M 0 5.3M 0% /run/lock
tmpfs tmpfs 517M Laravel Tutorial - Filemanager 0 517M 0% /sys/fs/cgroup
/dev/vda15 vfat 110M 3.6M 106M 4% /boot/efi
tmpfs tmpfs 104M 0 104M 0% /run/user/0

Code (markup):

I suppose that /dev/vda1 is my working partition I have 20 GB of free disk space I can use for my applications.
Is it so?


Now on my laptop there is Kubuntu 18 too, so I suppose that /dev/vda15 that is boot partition. I have general understanding what is it.

1) Just interesting : what are the rest of partitions and have I anyway to pay attention on them or take care about them ?

2) If there is safe way to restart Ubuntu 18 on Digital ocean droplet ? In some cases I modify some
config files, say of apache 2(I work with php) and I know that to apply my changes I need to run

sudo service apache2 restart

Code (markup):

But In some cases I do not know, if my changes are applied and I would prefer to restart my system as I usually do on my laptop...

Thanks!