DNS, short for Domain Name System, is the ‘phone book’ of the Internet. DNS servers eliminate the need to memorize IP addresses such as 192.168.0.1 (IPv4), or the newer alphanumeric IP addresses such as 2400:cb00:2048:1::c629:d7a2 (IPv6).
OmniNet does not block access to ISP provided services (Comcast/Xfinity, AT&T, etc).
Most ISP’s do not allow other ISP’s to use their DNS servers or other services. When they see traffic from other ISP’s the response is to either throttle or block that traffic.
ISP’s could sell browsing history and DNS requests. Most say they do not, however it is still a concern to some researchers.
It is highly recommended to use vetted third party DNS servers such as ones provided by Quad9, CloudFlare, OpenDNS, and other privacy based companies.
A better question is ‘should I use ISP provided DNS servers’?
Most security minded companies heavily advise against using ISP DNS servers as there are much better options.
While OmniNet does not endorse any particular companies some of the most reliable are from Google, CloudFlare, and OpenDNS.