If your new to blockchains you might not know of all the places you can look to follow the projects you are watching. Most people tend to only check their projects websites, Telegram group and Medium spaces.

You can get a lot of behind the scenes progress for aelf on Github. https://github.com/AElfProject/AElf

Here in Github you will find information on aelf from conception to the latest fixes, additions and improvements.

In the repository you will find the code that aelf is using to run their nodes and the command line tools used to interact with them. It also contains a tests folder that centralizes all the unit tests.

aelf welcomes anyone that would like to run a test side chain or contribute in a positive way to improving our blockchain. In order to do this you will need to have a good understanding of how to work with C#.
aelf appreciates other types of contributions such as documentation improvements or even correcting typos in the code if you spot any.

aelf expects every contributor to be respectful and constructive so that everyone has a positive experience, you can find out more about of code of conduct at the following address.  https://github.com/AElfProject/AElf/blob/dev/CODE_OF_CONDUCT.md

Go to Github today and check out the great progress aelf has made and is continuing to make each day.
 

Let's start with What is a Sidechain:
A Side chain allows tokens from one blockchain to be securely used in a separate parallel blockchain. Tokens can still be moved back to the original chain if necessary. Think of it like how a car driving in the express lane can merge back into the regular highway lanes.

Now that we have the definition of a Side chain, how does aelf's Side chains work?

aelf consists of one Main Chain and multiple Side Chains attached to the Main Chain. This differs from a traditional Single Chain system in that aelf is a "branched eco-system" where the Main Chain works as the backbone of the system and connects to multiple Side Chains (this can even include multiple layers).

In the aelf blockchain each Side chain is dedicated to one type of contract and resolves one type business problem. By dedicating one chain to one contract this allow for tailoring the needs of the commercial requirements of any given business.

When the need arises a branch is created and a new Side chain is made, by doing this it allows for new functions and maintains an "easy to use structure"

In this structure Side chains do not talk to each other. Verification of aelf Side chains is provided by the Main Chain.

This is what makes aelf Blockchain unique and ever evolving.

akristofor aelf has a very unique blockchain framework. In that every side chain will have only one contract, this will allow for faster transaction times.

If you haven't done so yet please give their white paper a read. https://aelf.io/gridcn/aelf_whitepaper_EN.pdf?v=1.6
You can also join the community in Telegram at https://t.me/aelfblockchain

My 3 exchanges are:
Binance
Bibox
Coinex

Timerland to answer your 1st question.
I have been working for aelfblockchain since early 2018. I have had a bitcointalk account since then but have not used it until now.

As elda34b has stated those are some of the exchanges where the community can purchase elf tokens.

There is a video from 2018 where Michael Arrington and Zhuling Chen discuss aelf and blockchain in general.
https://youtu.be/v0puMd1xGRA

Quick recap of aelf:
The core principle of aelf is to resolve practical technical issues that have been tested already. Attention to making mature configurations that will stabilize business applications when the are executed. aelf will have one main-chain with infinite side chains. Each side chain will work on one and only one contract at a time.

What is a dApp? -They are a type of software program designed to exist on the Internet in a way that is not controlled by any single entity. dApps are a ‘blockchain enabled’ website, where the Smart Contract is what allows it to connect to the blockchain.

In order for an application to be considered a dApp in the context of Blockchain, it must meet the following criteria:

 The Application must be completely open-source.  It must operate autonomously, and with no entity controlling the majority of its tokens. The application may adapt its protocol in response to proposed improvements and market feedback, but the consensus of its users must decide all changes.
   
The Application data and records of operation must be cryptographically stored. It must be cryptographically stored in a public, decentralized blockchain in order to avoid any central points of failure.
   
Also the application must use a cryptographic token. (Bitcoin or a token native to its system) which is necessary for access to the application and any contribution of value from (miners/farmers) should be rewarded with the application’s tokens.

The application must generate tokens, according to a standard cryptographic algorithm acting as a proof of the value, nodes are contributing to the application (Bitcoin uses the Proof of Work Algorithm).

Dapps can be used for anything from Banking to medical records to any type of gaming app.

So what dApps do you envision on the aelf Blockchain?
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