What is the difference between internal and external modem

Internal modems are commonly found as expansion cards that are installed inside a computer. They usually connect to the motherboard using a PCI or ISA slot. These modems are not visible externally and are integrated into the computer's hardware.
External modems, on the other hand, are separate devices that are connected to the computer externally. These modems are typically plugged into a serial port on the computer or connect using a USB port. They are not installed inside the computer's casing like internal modems.
In summary, the main difference between internal and external modems lies in their physical connection to the computer. Internal modems are expansion cards installed inside the computer, while external modems are separate devices that connect to the computer externally.