Electronic Travel Authority (ETA) and the ETA Visitor:
The Govt. of Australia says that:
An ETA is equivalent to a visa, but there is no stamp or label in your passport and there is no need for you to visit an Australian diplomatic office to submit an application. Applications for ETAs can be submitted through travel agents or airlines.
In a small number of cases, if your ETA cannot be approved immediately, you will need to check back in 12 hours to confirm whether your application has been successful. You can also check your ETA status, if you applied through this site, by clicking on the Check your ETA button.
The ETA is issued electronically by a computer system operated for the Department of Immigration and Citizenship (DIAC) of Australia.
When an application for an ETA is submitted through this site, all you need to do is enter the details from your passport and your credit card information. The application is processed immediately. Approved applications are electronically recorded on Australian Government systems.
When you arrive at an airport for check-in on a flight to Australia, the airline check-in staff can electronically confirm that you have authority to board the flight to Australia.
There are two following types of this visa where we can apply online
1. Visitor ETA
In this visa if one is ramble for tourism or to visit friends or relatives, one should apply for this visa which is called Visitor/Tourist ETA. It is officially valid for twelve months with stays of up to 3 months on each visit, and can be used for single or multiple entry travel. job is prohibited with this visa.
2. Short Validity Business ETA
If you are going for business matters, you should apply for the SVB ETA. It is officially legitimate for 12 months with stays of up to 3 months on each visit, and can be used for single or multiple entry travel. Employment is strictly forbidden.