Explanation
The Data Import Wizard and the Data Loader are both tools that can import data into Salesforce and assign records to a queue or run an active assignment rule1. The Data Import Wizard can import up to 50,000 records at a time, while the Data Loader can import up to 5 million records at a time2. Both tools can also prevent duplicates by matching records based on external IDs or Salesforce record IDs3.