Comprehensive and Detailed Explanation:
Steganography allows someone to hide data (like a spreadsheet or document) within another innocuous- looking file (like an image, video, or audio). This disguises the presence of the data entirely, allowing it to bypass standard data loss prevention (DLP) systems and firewalls, which look for file types and suspicious patterns.
From CEH v13 Courseware:
* Module 6: Malware Threats # Steganography and Covert Channels
Reference:CEH v13 Study Guide - Module 6: Data Hiding Techniques Using SteganographyNIST SP 800-83
- Guide to Malware Handling and Prevention

Webhooks are one of a few ways internet applications will communicate with one another.
It allows you to send real-time data from one application to another whenever a given event happens.
For example, let's say you've created an application using the Foursquare API that tracks when people check into your restaurant. You ideally wish to be able to greet customers by name and provide a complimentary drink when they check in.
What a webhook will is notify you any time someone checks in, therefore you'd be able to run any processes that you simply had in your application once this event is triggered.
The data is then sent over the web from the application wherever the event originally occurred, to the receiving application that handles the data.

Here's a visual representation of what that looks like:
A webhook url is provided by the receiving application, and acts as a phone number that the other application will call once an event happens.
Only it's more complicated than a phone number, because data about the event is shipped to the webhook url in either JSON or XML format. this is known as the "payload." Here's an example of what a webhook url looks like with the payload it's carrying:

What are Webhooks? Webhooks are user-defined HTTP callback or push APIs that are raised based on events triggered, such as comment received on a post and pushing code to the registry. A webhook allows an application to update other applications with the latest information. Once invoked, it supplies data to the other applications, which means that users instantly receive real-time information. Webhooks are sometimes called
"Reverse APIs" as they provide what is required for API specification, and the developer should create an API to use a webhook. A webhook is an API concept that is also used to send text messages and notifications to mobile numbers or email addresses from an application when a specific event is triggered. For instance, if you search for something in the online store and the required item is out of stock, you click on the "Notify me" bar to get an alert from the application when that item is available for purchase. These notifications from the applications are usually sent through webhooks.

In CEH v13 Module 12: Hacking Web Applications, the N-tier architecture is explained as a model used in web applications, typically with:
Presentation tier - User interface (UI) that interacts with the user.
Logic tier (also known as application or business logic layer) - Processes commands, makes logical decisions, and handles data movement and processing between the UI and the database.
Data tier - Manages database access and data storage.
So, the Logic tier is responsible for:
Handling the business rules.
Processing user inputs.
Accessing and manipulating data from the database.
Reference:
CEH v13 Module 12 - Web Architecture Concepts
CEH iLabs: Application Logic Testing Exercises

http://www.carnal0wnage.com/papers/LSO-Hping2-Basics.pdf
Most ping programs use ICMP echo requests and wait for echo replies to come back to test connectivity.
Hping2 allows us to do the same testing using any IP packet, including ICMP, UDP, and TCP. This can be helpful since nowadays most firewalls or routers block ICMP. Hping2, by default, will use TCP, but, if you still want to send an ICMP scan, you can. We send ICMP scans using the -1 (one) mode. Basically the syntax will be hping2 -1 IPADDRESS
* [root@localhost hping2-rc3]# hping2 -1 192.168.0.100
* HPING 192.168.0.100 (eth0 192.168.0.100): icmp mode set, 28 headers + 0 data bytes
* len=46 ip=192.168.0.100 ttl=128 id=27118 icmp_seq=0 rtt=14.9 ms
* len=46 ip=192.168.0.100 ttl=128 id=27119 icmp_seq=1 rtt=0.5 ms
* len=46 ip=192.168.0.100 ttl=128 id=27120 icmp_seq=2 rtt=0.5 ms
* len=46 ip=192.168.0.100 ttl=128 id=27121 icmp_seq=3 rtt=1.5 ms
* len=46 ip=192.168.0.100 ttl=128 id=27122 icmp_seq=4 rtt=0.9 ms
* - 192.168.0.100 hping statistic -
* 5 packets tramitted, 5 packets received, 0% packet loss
* round-trip min/avg/max = 0.5/3.7/14.9 ms
* [root@localhost hping2-rc3]#