
Importing data with Data Loader
Data Loader is a standalone application that's used to bulk import (and export) data. It can actually do all kinds of CRUD operations (insert, update, delete, and export).
To download the app, go to Setup | Integrations | Data Loader and select the download link for your operating system (Windows or macOS). The documentation links are also available on this page.
There is even a SaaS version of Data Loader called dataloader.io. It can be downloaded for free, but there will be some limitations regarding what features you can use. Alternatively, you can get the full-featured version if you're willing to pay for additional licensing costs (https://dataloader.io/).
Data Loader can be used via its user interface or through the command line to ease the task of automated export/imports. Let's say you have an external billing service that stores in a remote server all the bills created daily, as a CSV file. With a scheduled job on the server, you can enable Data Loader so that it loads this CSV file into Salesforce automatically (supported for servers running Windows only).
You should use Data Loader when you want to load a standard object that is not supported by the Data Import Wizard, or when you want to schedule a lot of data to be uploaded or an export on a regular basis (using the command line).
You may also need to load around 50,000 to 5,000,000 records (you can use it to load one record; there's no limitation on the lower end of the scale), but if you need to bulk update more often, you'll need an external solution, which you can find at AppExchange (http://appexchange.salesforce.com/).
We won't talk about this tool extensively in this book, so please refer to Salesforce's official Data Loader guide at https://resources.docs.salesforce.com/218/latest/en-us/sfdc/pdf/salesforce_data_loader.pdf if you wish to find out more. If you want a quick glimpse at what you can do with Data Loader, please refer to this awesome post by Salesforce Ben: https://www.salesforceben.com/introduction-to-the-salesforce-data-loader/.