One of the unique features of Lokalise is the ability to use similar keys across different platforms, thus reducing the amount of translation work to be done by translators. Once you import or add keys, they need to be assigned to one or several platforms (e.g. iOS, Android).
Assigning a key to a platform actually means including the key in the export routine for the file formats compatible with this platform. For example, if the key is assigned to both iOS and Android platforms, it would be exported to Apple .strings and Android .xml, however it would not go to a Web .json export (while keys with a Web platform would only go to a .json export). You can think of platforms as global tags for the keys. In the case that you want all the keys to be exported regardless of the platform (e.g. you need to export all to Excel), just turn on the "Include all platforms" option on the project download web panel.
Different keys for different platforms
Coding for different platforms usually involves different naming schemas, for example iOS coders prefer "LoginButton", while Android coders are keen on "login_button". Lokalise has the solution to this never-ending battle. Enable "Per-platform key names" in project settings, then once you add a new key (or edit the imported one) there is an option to set a unique key name per platform.
Hidden and archived keys
If you are not done editing your original translation, mark the key as "Hidden from contributors" so contributors can't see it and don't start the translation. Note, that other project admins will see this key and its translations.
You may want the option to archive keys so they are not visible in statistics, export, search and similar areas. Archived keys can be found by choosing "Archived" in the Filter. In order to archive or unarchive keys, select the desired keys in editor view (by selecting a checkbox to the left of the key) and choose the appropriate action from the floating box.