Crossover cables can support direct communication between two computers without the need for an intermediate device. Keep in mind this just refers to the cable, the computers still need to be correctly configured for this to work. Many modern Network Interface Cards (NICs) can support automatic cable type detection allowing a Crossover and Straight-through cable to work. A Rollover cable is used to connect a computer to network devices for configuration purposes only and is sometimes called a console cable. RJ-11 and RJ-45 are connector types not cable types.
An Ethernet crossover cable is a crossover cable for Ethernet used to connect computing devices together directly. It is most often used to connect two devices of the same type, e.g. two computers (via their network interface controllers) or two switches to each other. By contrast, straight through patch cables are used to connect devices of different types, such as a computer to a network switch.
Intentionally crossed wiring in the crossover cable connects the transmit signals at one end to the receive signals at the other end.
Many network devices today support auto MDI-X (aka "auto crossover") capability, wherein a patch cable can be used in place of a crossover cable, or vice versa, and the receive and transmit signals are reconfigured automatically within the device to yield a working connection.