One of the key factors in Visio’s success over the last 15 years or so, has been its capability to connect one shape to another. This is an essential factor in creating useful business diagrams, such as organization charts, process flows, and network diagrams. Over the years, Visio added the capability to create database entity relationships, UML, and brainstorming diagrams, among others. Together with the capability to store data with each shape, Visio defined a new data-diagramming paradigm, which others have struggled to emulate.
You can create connections between shapes using many methods. Most of them involve using a 1-D shape (one-dimensional line) to connect between two 2-D shapes (two-dimensional boxes). These connections can be Dynamic (no need for a connection point in the 2-D shape) or Static (glued to a connection point in the 2-D shape or page).
Unfortunately, in the 2003 version, Microsoft decided to retire two of the most used wizards, which were able to create certain types of network diagrams or to read the connections from a diagram back into a database.
At some point, the Visio development team recognized the need to connect two 2-D shapes together in uses such as laying out office worktops or HVAC ductwork, so they also added this capability.
In all these cases, the visual connection of shapes can represent the logical or physical connection of the elements these shapes represent, such as the reporting hierarchy in an organization, the flow of a process, or the cable between an outlet and a PC. Some of these connections have a direction, often represented by arrows, and some may represent different types of connections, often indicated by changing the line type or color.