Is the ESTA a visa?
Actually, it is not. Despite the fact that the ESTA is generally known as a “visa” the VWP performs the inverse process, allowing visitors to not require a visa as a “non-immigrant person” to enter the United States.
Therefore, if you want to enter the USA for reasons concerning part-time or full-time work, you have to request a visa as a non-immigrant person from the offices involved in the process. This regulation also applies to people looking for a permanent residence permit. This will be different from an ESTA application.