Device interfaces
Common standards are often used to connect a wide variety of device pairs.
Universal serial bus
USB is currently most popular. USB 3 enables superior data-transfer speeds.
USB allows for a tiered star topology: so one can connect many devices to a particular device with a single usb wire branching out into many others. Power dissipation limits the extant to which this can be done.
USB Plugs
USB wires have 4 (sometimes 5) terminals arranged in various shapes.
Type A is most common.
Micro B is a small trapezoid - often used with pocket computers.
Mini A and B are also sometimes used.
Type B is used with monitors.
Modems
Modems provide a link to a wider network - usually the Internet. They differ based on the means of communication used in providing this link, and the links it can provide to devices seeking connection to the wider network.
Mobile Wifi (MiFi)
These connect to the wider network using 3G or 4G compatible protocols; and allow devices to connect to it using WiFi protocol - for which reason, they are called ‘hotspots’.