TShock is a toolbox for Terraria servers and communities. That toolbox is jam packed with anti-cheat tools, server-side characters, groups, permissions, item bans, tons of commands, and limitless potential. It's one of a kind.
Any version older then TShock v5 needs to use the legacy egg, and version newer or v5 must use the normal TShock one.
## Migration from v4 to v5
If you're upgrading from TShock 4, you swith to the new egg copying the tshock configuration folder over (containing the sqlitedb file as well as the json configuration files, etc) to the new server, and starting the new server that way.