Putty is an open source Linux program for accessing the server. Something like Filezilla, but with Linux code. It requires SSH access. With Putty, you can use Composer. Composer is essential for Drupal 8.
Beside Putty you can use FireSSH (Firefox), Secure Shell Extention (Chrome) or Terminal (Mac). Terminal users log in with (ssh firstname.lastname@example.org).
Every hosting has his own rules about SSH. Sometimes you need to ask the support of the hosting to give you SSH access (Vimmex). They will do it without any problem. Some hostings do not provide ant SSH access at all... Inform yourself before you install a Drupal 8!!!
With a Neostrada hosting you can do it yourself. Go to the Control Panel en click on SSH Access.
Click on Manage SSH Keys.
Generate a New Key.
Choose a pasword.
Done. You see the keys now.
Now you need a program to access the server. Putty is popular.. Install.
Fill in your hostname and port (see the FAQ of the hosting for that)
In my case.
They ask if the key has to be stored..
Now you can log in, using your CP username and password. You don't need the SSH key.
When writing the password, nothing will appear.. Just continue..
When you type dir (=directories) you will see all the folders and files. If you want to go to a folder type cd. To return type cd ../
Go to the public_html map: 'cd public_html'. Composer is already installed, during the Drupal 8 installation! Try the list command. If you see all of the commands you are in the right folder. Don't be dissapointed.. You only need a few commands to set up your Drupal 8. The most important will be require.