A Townbloc or Voting Bloc (shorthand, "bloc") is a group of players that vote together during the day. The existence of a Townbloc does not need to be public knowledge for it to operate as one. There's no single point that defines the beginning of one, though its being is precipitated upon a period of cooperation of those involved.
It's important to know that a Townbloc is not always comprised of Town-aligned players, just simply people perceived to be so. Votes are also not necessary - having a period of sharing reads and progressing the game is also sufficient for a group of players to be described as a Townbloc. In Mini 1869: Camn's Revenge featured a lengthy period of 18 pages where all or nearly all posts were made by the town, beginning at post #1555.
The history of Townblocs has seen a debate of blocs that are manufactured versus ones that occur organically. While some players go to great lengths to create one, its existence comes before any proof of one, leaving itself open to questions of whether it is a legitimate townbloc. Attempts to create one must be made carefully, or doubt could stop any work the group could perform together.