Connecting machines means creating a communication channel between machines so that they can exchange information with each other. The channel can be wired or wireless (WiFi, Bluetooth, ...)
Digital communication channel means that the information exchanged can be translated into binary information, i.e., as sequences of 0's and 1's, i.e. numbers.
The advantages of having digital communication are that it can automate actions following certain events, it can store information, it can make this information understandable to a computer, and it can transform it. In addition remote control is possible. The disadvantages are that for the use of such machines it is necessary to address all the computer security issues that plague computers. As a result, when such a machine is placed in a production environment, a risk analysis and an assessment of what, if any, actions need to be taken to mitigate or avoid the damage caused by any computer security issues.