What is the difference between ESTA and the US visa?

The US visa system has been in place as far back as 1924 for any non-citizen to visit the US. Since then, the system has developed to help control the criteria for immigration to the US and to protect the US workforce, as well as forming a part of the border security control framework.
The visa system has seen many changes and includes the introduction of the ESTA (Electronic System for Travel Authorization) which applies for visitors travelling to the US under the Visa Waiver Program (VWP).The VWP includes a list of countries from which citizens are eligible to apply for an ESTA as opposed to applying for a different form of visa. For citizens that are not in the countries listed under the VWP, they must apply for a US visa instead.

Difference in purpose of visit

There are many differences between an ESTA and other US visas. Firstly, an ESTA is only for tourism, business and transit purposes and ESTA holders are not permitted to work or study in the US unless they obtain a different form of visa, such as a working or student visa.
There is a long list of different visa types that cover various types of purpose such as temporary workers, nurses, business visitors and many more. The type of visa that a person applies for depends on the criteria under each one and there are many requirements under the US visas such as providing proof of finance, qualifications and other documentation as part of the approval process.

Length of validation of ESTA vs US visa

When an ESTA is issued it is valid for a period of two years, or until the passport that it is linked to expires (whichever date is the sooner). A US visa will have a different length of validity depending on the type of visa, for example a student visa will be granted for the length of study.
Whilst the ESTA is valid for two years, it only permits a visit to the US for 90 days maximum in any one visit. However, multiple visits to the US are covered under the two-year validity, without the requirement to apply for a new ESTA.

Application processing differences

An ESTA is considered to be the easier way to get permission to visit the US, as the application process is very short. The applicant simply needs to complete an online form that consists of a few pages, which generally takes no more than 10 minutes to complete and submit. The applicant is required to provide personal information, passport details and any details about criminal convictions or health issues, if relevant. Usually the ESTA will be processed in just a few hours and is ready to be used for travelling to the US, as it automatically links electronically to the holder’s passport.
A US visa on the other hand will usually require the applicant to visit the US Embassy in their home country for an interview to determine whether their application will be approved. The process can take weeks and in some cases where lots of documentation and evidence is required, it can even take months to process a US visa.
The application fee for a US visa is considerably more expensive than an ESTA, with most non-immigrant visas costing $160 to apply. An ESTA application costs much less.