If you intend to study in Australia, you will need to apply for a Student visa (subclass 500). If you are the parent, guardian or relative of a student, you can apply for a Student Guardian Visa (subclass 590). If you would like to travel to Australia for a visit and short-term study, you may be eligible for a visitor visa. A Training Visa (subclass 407) allows you to take part in workplace-based training to enhance your skills in your current occupation, area of tertiary study, field of expertise. A Temporary Activity Visa (subclass 408) permits temporary entry into Australia for certain programs and projects.

A social security card is used in the U.S. as way to prove your identity. Each social security card has a 9-digit social security number (SSN). This number is unique to each person and used for the purpose of tracking an individual in the U.S. Social Security Administration. All people who work in the U.S. must have a SSN. SSNs are mostly used for tax purposes.
Some countries, such as Canada and the United States, may require the visitor to include a letter of invitation with their travel visa application. A letter of invitation is a formal letter from the person you intend to visit stating that they are inviting you to visit them in that country. Invitation letters help travel authorities vet potential visitors by making sure that a temporary visit is indeed the true nature of the visa request. Check with your intended destination’s government website for details on what needs to be included in a such a letter.
Imagine your own ties in the country where you live. Would a consular office of another country consider that you have a residence there that you do not intend to abandon? It is likely that the answer would be "yes" if you have a job, a family, if you own or rent a house or apartment, or if you have other commitments that would require you to return to your country at the conclusion of a visit abroad. Each person's situation is different.
A work permit, or Employment Authorization Document, is proof that a person has permission to work in the U.S. People with work visas are eligible for work permits and must obtain one before starting work in the U.S. If you have another type of temporary visa, such as an F-1 visa, you may also be eligible for a work permit. Learn more about work permits.
Some countries, such as Canada and the United States, may require the visitor to include a letter of invitation with their travel visa application. A letter of invitation is a formal letter from the person you intend to visit stating that they are inviting you to visit them in that country. Invitation letters help travel authorities vet potential visitors by making sure that a temporary visit is indeed the true nature of the visa request. Check with your intended destination’s government website for details on what needs to be included in a such a letter. 

At present, 38 countries in the Visa Waiver Program are Andorra, Australia, Austria, Belgium, Brunei, Chile, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, the Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovenia, Slovakia, South Korea, Spain, Sweden, Switzerland, Taiwan and the United Kingdom.
Tourist visas, called visitor visas in the United States, are available for travelers from many countries who are coming for recreational or medical purposes. These visas are typically good for six months. Transit visas are available to foreigners who are simply passing through the United States or making a brief stop at a port or airport. Transit visa applicants must provide evidence that they will be in continuous transit to a foreign destination while in the United States. As of November 2012, both visitor visas and transit visas cost $160 per person, although additional fees may apply. Citizens of nearly 40 countries are allowed to travel in the United States without a visa under the Visa Waiver Program.

The United States is an open society. Unlike many other countries, the United States does not impose internal controls on most visitors, such as registration with local authorities. Our immigration law requires consular officers to view every visa applicant as an intending immigrant until the applicant proves otherwise. In order to enjoy the privilege of unencumbered travel in the United States, you have a responsibility to prove you are going to return abroad before a visitor or student visa is issued.

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