REST API is used when the number of records are very less.
Bulk API is used when we are going to implement for large set of data. Bulk API also uses the same principles of REST API.
Use the Bulk API for more than 50,000 records or for time-sensitive loads that can take advantage of very large batches. BULK API use GET method to get data and POST data for DML operations.
To create a Job(set of records to process), we have to send the POST request to the below URI
https://instance.salesforce.com/services/async/APIVersion/job
Content Types allowed in BULK API
1. CSV(recommended)
2. XML
3. ZIP_CSV(binary attachment)
4. ZIP_XML(binary attachment)
BULK API doesn’t support login(). We have to use SOAP API for login.
Cheers!!!