Modem
A modem is needed in order to connect to a dial up internet connection. A
modem can also be used for faxing. Modems can attach to the computer in
different ways, and can have built-in processing or use the computer’s CPU for
processing.
Modems with built-in processing generally include all modems that connect
via a standard serial port, as well as any modems that refer to themselves as
“Hardware Modems”. Software Modems, or modems that rely on the CPU generally
include both Internal and USB modems, or have packaging that mentions
drivers or requiring a specific CPU to work.
Modems that rely on the CPU are often designed specifically for the current
version of Windows only, and will require drivers that are incompatible with
future Windows versions, and may be difficult to upgrade. Software Modems
are also very difficult to find drivers for non-Windows operating systems. The
manufacturer is unlikely to support the hardware with new drivers after it is
discontinued, forcing you to buy new hardware. Most such modems are internal
or external USB, but this is not always the case.
Modems can be attached via USB, a traditional serial port, or an internal
card slot. Internal and USB modems are more easily autodetected by the operating
system and less likely to have problems with setup. USB and serial port
modems often require an extra power supply block.
Gaming modems are normal modems that default to having a low compression
setting to reduce lag, but are generally no longer used by gamers, who
prefer broadband connections.

Ethernet card
An ethernet card is required in order to connect to a local area network or a
cable or DSL modem. These typically come in speeds of 10Mbps, 100Mbps, or
1000Mbps (gigabit); these are designated as 10Mbps, 10/100Mbps, or 10/100/1000Mbps
products. The 10/100 and 10/100/1000 parts are most commonly in use today.
In many cases, one or two ethernet adapters will be built into a motherboard.
If there are none, you will have to purchase one—these typically are inserted
into a PCI slot. To get the full speed of 10/100/1000Mbps ethernet, it’s best to
get a motherboard with that connector built in.