The E2 visa is for entrepreneurs and business owners from Treaty countries who wish to make a substantial investment in an American business, either through setting up a new enterprise or by investing in an existing US entity
The B1 visa is a non-immigrant visa, specifically designed for temporary business visits to the USA.
To enter the USA as a visitor, any non-US national must either have permission under the Visa Waiver Programme or hold a relevant visa. Whichever of these options applies, you must also have a valid passport.
Contrary to come misconceptions, ESTA (Electronic System for Travel Authorisation) is not a visa. Where an individual is eligible to enter the USA under the Visa Waiver Programme (VWP), they must first hold ESTA approval before they can travel to the US.
Foreign nationals wishing to travel to the USA will in most circumstances be required to hold a valid US visa to accompany their passport in order to gain entry and to remain into the country.
When a foreign national wishes to visit the USA, whether on a temporary or permanent basis, they will need to make a US visa application if they are not eligible for the visa waiver program.