As the name implies, an input device is an object, gadget, or device that lets a person put information into their computer. As other Educators have already noted, keyboards and mouses (or touchpads) are clear examples of input devices. They're tools that allow users to send data and orders to their computer. If someone wants to tell their computer to go to a specific website, they can do so thanks to input devices. Using the mouse (or touchpad) and keyboard, they can make their computer call up that site.
Of course, many people have phones that function like computers. If someone wanted their phone to go to a certain website, to play a specific song, or send a text, they’d need input devices as well. That input device might be their touch screen. If they’ve bothered to set up speech recognition, they could also use their voice. They could tell their phone to go to a certain website, play a certain song, or send so-and-so a text.
In the context of speech recognition, giving a phone, computer, and so on input resembles the way people give other people input. They both use their voice to relay information and instruction. Of course, people don’t automatically have to follow another person’s input. However, when it comes to Siri, Alexa, and so on, if they don’t follow a person’s input, they’re probably not functioning properly.