Early voting allows you to vote before election day. Most states allow in-person early voting during a designated period of time before Election Day.
Source: usa.gov
Missouri does not have early voting but allows for in-person absentee voting, "which is when a voter requests, completes and signs an absentee ballot in a polling place. From the voter’s perspective, however, the experiences of early voting and in-person absentee voting are essentially the same."
Source: NCSL
Source: usa.gov