The 601 visa will get granted with multiple entry for a total of 12 months, or how long your passport is valid for, whichever is the shorter. You can leave and enter Australia as many times as you want while your 601 visa is valid and stay for up to 3 months at a time.
To be eligible for this visa, you must hold a passport from an eligible country and intend to stay in Australia to visit only. With this visa you are not allowed to work, so you must make sure that you have enough funds to support yourself during your stay.
You must be outside Australia when you apply and when a decision is made on your application. It is not possible to include family members in your application. Each family member must apply separately. If you wish to extend your stay in Australia, you can apply for another visa. See here if your country of passport is eligible.