If you are looking to apply for an ESTA visa, then it is important that you follow the official application process. There are many fake sites that offer ESTA visa application services. These sites could delay your application and will cost you more money even though they do not do anything of value.
The official ESTA visa application process is performed on the official .gov website. There is a fee required for processing your application. There is no need to pay any third parties to check your application before sending it, however, because the government website does the same thing, and your application will be processed more quickly if you go straight to them.
The ESTA is not actually a visa. Rather, it is an authorization to travel. You will still need to meet the other criteria to come to the USA, depending on the country that you are traveling from and the nature of your trip. If you are not sure whether you can enter the country under the Visa Waiver program (which is who the ESTA is for), then you can check online or with the embassy. Do this before you make travel arrangements, just in case there are any issues with your application.
The ESTA is aimed at people who are traveling for 90 days or less, and it can be used by citizens of countries that are a part of the Visa Waiver program who are traveling for business or for pleasure. It is usually processed quite quickly, but because of the possibility of delays it is a good idea to apply as soon as you are considering entering the United States. You do not need to have firm travel plans when you apply, although if you do know your dates of travel it is helpful to apply them.