If you are traveling to the United States from another country, you will need to get a visa or an ESTA (Electronic System for Travel Authorization) depending on what country you are from.
You should be eligible to get an ESTA if you are a citizen or national of the following countries: Andorra, Australia, Austria, Belgium, Brunei, Chile, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, the Netherlands, New Zealand, Norway, Poland, Portugal, San Marino, Singapore, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, Taiwan and the United Kingdom.
If you are not a citizen or national of one the countries listed above, you will need to apply for a visa.
Here is a great tool to determine if you are eligible to apply for a visa or ESTA.
https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/wizard.html
Please note, you are responsible for paying any associated fees in obtaining an ESTA or visa. The cost for an ESTA as of September 2023 is $21 USD. The cost for a visa as of September 2023 is $185 USD.