"HiFi" refers to high quality sound reproduction - you can see this Wikipedia page to learn more about this. Regarding Rango Broadband, the term "HiFi" is simply how their Internet plans are called.
Hi marianliu07, I'm actually with Rango. We would love to get you set up so you can see for yourself how it works. We have no commitment and right now are offering free installation, so you really don't have anything to lose by giving it a shot. Once you do, we'd love to get your feedback as well. Feel free to reach out and we can go over all the options.