The U.S. Customs and Border Protection (CBP) is an agency of the U.S. Department of Homeland Security, founded on March 1, 2003. Its current headquarters are located in the Ronald Reagan Building in Washington, D.C.
The first mission of this agency is to prevent terrorist intrusion into the territory of the United States and the introduction of weapons (hence the link with ESTA).
CBP also has a role to play in contesting illegal immigration to the United States. This agency also deals with the British equivalent of Customs, it fights against the introduction into the United States of drugs, smuggling and unauthorized products, such as agricultural products from tropical environments, which are subject to strong surveillance to prevent the spread of contamination. And of course, the protection of the intellectual property.
While its primary mission is to prevent terrorism and the entry of terrorist weapons into the United States, CBP is also responsible for arresting people seeking to enter the United States illegally, particularly those with a criminal record, combating the entry of drugs and other contraband products, protecting American agriculture and its economic interests against pests or other harmful diseases, and protecting the American economy from theft or counterfeit intellectual property.
It should be noted that ESTA is only required for nationals from countries covered by the Visa Waiver Program