Interfaces is the overall term for the external connections between a system and the world around it.
Wikipedia has an article describing computer interfaces as "the shared boundaries" over which information is exchanged.
The article goes on to describe a system design method called "programming to the interface", which can be generalized further to "design to the interface".
A good system design consists of developing system requirements, which begin with interface specifications and functional specifications. This is followed by partitioning into smaller, more manageable blocks (often called subsystems or blocks, but generically they are also systems), and specifying the interface and functional requirements of each partitioned block. In complex systems, to maintain design independence avoid propagation of problems across interfaces, designers focus on the limited requirements for the functions and interfaces of their subsystems. Chaos is avoided by documenting requirements in functional specifications and interface control documents before detailed design begins.
Interfaces include physical and logical connections between blocks.They include hardware connectors, electrical specifications, communications waveforms and protocols, software object properties and method signatures, spatial requirements (e.g. mounting requirements for hardware, including static devices and actuators). They also include human interfaces, like lights, buzzers, and video screens. Interfaces encompass all of these boundaries between a system and the world outside the system.