Your WhatsApp chats are automatically backed up and saved daily to your phone's memory. Depending on your settings, you can also periodically back up your WhatsApp chats to Google Drive. If you uninstall WhatsApp from your phone, but don't want to lose any of your messages, be sure to manually back up your chats before uninstalling.
Go to WhatsApp > tap More options > Settings > Chats > Chat backup > BACK UP.
You can use the export chat feature to export a copy of the chat history from an individual or group chat.
An email will be composed with your chat history attached as a .txt document.