Final answer:
Both online voting and absentee voting by mail allow remote casting of ballots; the main similarity is remote voting, while the difference is the medium of submission. Absentee voting is a paper-based and established process, while online voting is digital and experimental.
Step-by-step explanation:
One similarity between online voting and absentee voting by mail is that both methods enable voters to cast their ballots remotely without the need to physically go to a polling station. A key difference, however, lies in the medium of submission: while absentee voting is conducted through a mail-in paper ballot with varying levels of state support for applications and submission, online voting would involve electronically submitting a vote, akin to sending an email.
Furthermore, absentee voting is proven and widely utilized, including 'no-excuse' absentee voting and permanent absentee ballot lists in different states. In contrast, online voting is still considered experimental and faces significant concerns about voter fraud and ballot secrecy, leading to limited adoption and ongoing debates over its implementation.