When we talk about RJ45 ("Registered Jack" 45) we refer to a telecommunications network interface for wired connection of voice and data equipment.

This connector has 8 pins or connections and may have a specific category depending on the data transfer speed and bandwidth (category 5e, 6, etc.)

The common application is their use in Ethernet network cables under TIA/EIA-568-B standard that defines the arrangement of pins (pinout), but can also be used for other applications.

- Direct pin diagram:

EIA-568A
Pin No.1: WHITE-GREEN
Pin No.2: GREEN
Pin No.3: WHITE-ORANGE
Pin No.4: BLUE
Pin No.5: WHITE-BLUE
Pin No.6: ORANGE
Pin No.7: WHITE-BROWN
Pin No.8: BROWN

EIA-568B
Pin No.1: WHITE-ORANGE
Pin No.2: ORANGE
Pin No.3: WHITE-GREEN
Pin No.4: BLUE
Pin No.5: WHITE-BLUE
Pin No.6: GREEN
Pin No.7: WHITE-BROWN
Pin No.8: BROWN

- Schematic of crossed pins:

The crossover cable has one end with EIA-568A scheme and the other one with EIA-568B.

The Wifi technology is a wireless communication mechanism between devices. This technology allows you to connect devices such as computers, laptops, mobile etc... to the Internet or communicate with the devices themselves.

Applications can be several, among the most common are the access points, ideal for giving and sharing a connection signal to multiple devices. It is the typical configuration of a home user.
Repeater, ideal to repeat and amplify weak signal.

The power and range between devices basically depends on the antenna and its hardware.

The wireless signals work under a unified standard regulations, the standard that is based on the IEEE 802.11. These include IEEE 802.11b, IEEE 802.11g and IEEE 802.11n working at 11 Mbit/s, 54 Mbit/s and 300 Mbit/s, respectively.
Being any device with a standardized protocol such technology can connect to another using the same technology, making it a kind of universal connection.

The wireless networks are characterized by the ease and convenience of making connections in infrastructure, since it is not necessary to perform network cable installations.
it also allows connecting a lot of devices to a single node.