Layer 2 is the MAC address of the hardware. Layer 1 is the physical connection, and can be thought of as the actual voltages traveling across ethernet wires, or the raw binary data being transmitted by a wireless radio chip. The hardware is at the bottom layer of the network stack.

You can use the Network Stack to construct the right mental model for a network connection, and use it as a roadmap for figuring out how different technologies fit together. But how do all these protocols relate? How do you sort out what relates to what? There are other protocols as well, like SSH and VPN. The web server you connect to uses HTTP, hypertext transmission protocol, is the protocol used to compose the websites we visit in a browser. This uses an internet connection and a network of some kind that network is a TCP/IP network.

The chopped-up messages are called packets, and network devices (ethernet ports, wireless cards, network routers) are designed to send and receive packets. (Please Do Not Touch Steve's Pet Alligator) The physical medium for the network communication signals. Provides addressing scheme to identify physical devices, bridges, switches, MAC addresses. Handles packet fragmentation and error detection. Provide reliable data transport services to lower layers. Manages communication sessions between computers. Handles encryption/description for secure data Transforms data received into a format that is readable by the application layer.

Topmost layer, provides users a means to access network resources (only level seen by end user) That cascade - from the very high level down to the very low level - is broken down into the canonical seven layers of the network stack (from the Packet Analysis page): So all the HTML for the pages you're visiting, the Javascript libraries for the fancy graphics, the icons, the background images - all of that was broken into chunks of voltage, 0s and 1s, transmitted hundreds or thousands of miles by wire from switch to switch, to reach your computer. The communication of information between computers, however high-level it might be (a YouTube video of cats, say) must ultimately be broken down, chopped up, and send over the wire and across the internet to a server (and vice versa) using voltages - electrical 0s and 1s. Computers ultimately speak a single language, composed of two symbols: 0 and 1.

Wireshark http user agent browser