ISPs give consumers access to the internet (Access ISP) or lease server space that can be used via the internet (Host ISP). For VoIP, consumers need an Access ISP to connect to any hosted services. Network based VoIP systems may also need internet access to connect to telephone services or may be connected directly to the PSTN via a digital to analog gateway device.
Though there are many options for internet service providers available in the USA, the regulations for companies providing access to the internet often leave a location with no more than two to three options, rarely of equal value. Not the quality of competition one imagines in a free market, but great enough to have good options.
Currently, there are 3 main types of connections available: copper, wireless or fiber connections. Consumers often refer to them as DSL, W-iFi, and Broadband Cable. However, there are several other options in the categories, like VDSL, Satellite, and Wireless Broadband. Another note is that Wi-Fi is not actually an ISP option, but rather a range of devices such as modems or routers offering wireless connectivity.