In Drupal 7 you had the Localization update module (i10) and the Internationalization module (i18n) for building your multilingual site. Adding some flags with Language icons and done... In Drupal 8 everething except the flags are build in the core. The flags you still have to obtain with the Language icons module.
How do we start? During the installation you've been asked which language you want. Only this language is installed...Not really.. I think English is installed too but they don't show it. When you add English as a language, no translations are added. So.. the core is still in English. The following print shows the English language added after a Dutch installation.
It is important that you say to Drupal how to detect the language. At the bottom you see that the selected language is always available. A block has been made bij the core to switch languages. Give it a place. I prefer also that the language prefix detects the language. I can change the language of a node bij changing nl (stand for dutch) to en.
The language choise is a block. Give it a place.
For translating content types and nodes, adjust the language settings.
Then you can set the translation of the content type and the fields.
You can see the tab 'translate' editing the nodes. The content is default the original content with the original pictures. So it is your job to translate and to change the pictures if necessary. For each translation a new node is made. The nodes are connected to eachother though. When you look at a node an you change the language, your transation appears.
Views are a bit different. There is only one view. If you click on translate, for every item (field, filter, pagination,..) a translation is provided.
As an example you see a header of a view that has been transalated.
Translations of taxonomy terms are easy. Every term has his own translation button. Even a vocabulary can be translated.
Here is an example of a translated tag.
Sometimes translations are in the core system. Warnings for example. If not translated you can find them in the configurations. Here you see some items that have no translation. It is up to you to do it yourself..
With this tab you can see an overview of all translations.
Summary... Drupal 8 has a build in translation system. Cool. Everething you want to be translated has a translation tab. Drupal 8 is ready for multilingual sites.