Etydhv

I am pretty new in this ubuntu domain so please be gentle :o)
I wanted to remove my 'write' app, so I found this on a site:
To remove a package type:

sudo apt-get remove [package_name]

So I typed:

sudo apt-get remove [write]

And afterwards I agreed on the prompt: 'yes, do what I say!' or something like that. And voila! My Ubuntu was deleting!
Can anybody tell me why?

The correct command to remove a package named write is:

sudo apt-get remove write

[write] is a character set matching the characters “w”, “r”, “i”, “t” and “e” and as matching is done by substring by apt. The command you ran thus matched all packages with one of these characters in it, which of course are a lot. To quote apt’s output listing just the essential ones:

WARNING: The following essential packages will be removed.
This should NOT be done unless you know exactly what you are doing!
 apt adduser (due to apt) gpgv (due to apt) ubuntu-keyring (due to apt) libapt-pkg5.0 (due to apt) libc6 (due to apt) libgcc1 (due to apt) libgnutls30 (due to apt) libseccomp2 (due to apt)
 libstdc++6 (due to apt) base-files base-passwd libdebconfclient0 (due to base-passwd) bash libtinfo5 (due to bash) debianutils (due to bash) bsdutils libsystemd0 (due to bsdutils) coreutils
 libacl1 (due to coreutils) libattr1 (due to coreutils) libselinux1 (due to coreutils) dash dpkg (due to dash) diffutils libbz2-1.0 (due to dpkg) liblzma5 (due to dpkg) libzstd1 (due to dpkg)
 zlib1g (due to dpkg) tar (due to dpkg) e2fsprogs libblkid1 (due to e2fsprogs) libcom-err2 (due to e2fsprogs) libext2fs2 (due to e2fsprogs) libss2 (due to e2fsprogs) libuuid1 (due to e2fsprogs) fdisk
 libfdisk1 (due to fdisk) libmount1 (due to fdisk) libncursesw5 (due to fdisk) libsmartcols1 (due to fdisk) findutils grep libpcre3 (due to grep) install-info (due to grep) gzip hostname init
 systemd-sysv (due to init) init-system-helpers (due to init) perl-base (due to init-system-helpers) libc-bin login libaudit1 (due to login) libpam0g (due to login) libpam-runtime (due to login)
 libpam-modules (due to login) mount util-linux (due to mount) ncurses-base ncurses-bin sed sysvinit-utils libudev1 (due to util-linux)
0 upgraded, 0 newly installed, 2503 to remove and 0 not upgraded.
After this operation, 7238 MB disk space will be freed.
You are about to do something potentially harmful.
To continue type in the phrase 'Yes, do as I say!'

The multiple warnings as well as the necessity to literally type:

Yes, do as I say!

are security means in place to keep you from destroying your system, as the system’s package manager apt is perfectly capable of doing that. Any command run with sudo should be run carefully and thoughtfully, but don’t fret: Nearly every experienced user of Ubuntu broke their system at least once, in fact that’s part of the fun if you ask me.

Further reading

• 
  this answer to apt-get remove with wildcard removed way more than expected. why?