Dogecoin is a fun, new and rapidly growing form of digital currency. This form of digital currency is called "cryptocurrency"; a type of digital currency. Cryptocurrency is completely anonymous, decentralized, and extremely secure.

You can use it to buy goods and services, or trade it for other currencies (both other cryptocurrencies or traditional currency like US dollars or Euros).

Dogecoin is a cryptocurrency with a “doge” a short lived internet meme as its logo.Its a Japanese shiba inu dog popularized by an internet meme in 2010. Created in 2013 and quite similar to Litecoin. It is an open source peer to peer digital currency and effectively the 3rd most popular cryptocurrency after Bitcoin and Litecoin. It is a new and fun cryptocurrency rapidly growing. Like other cryptocurrencies it is also decentralised. Besides being completely anonymous it is extremely secure.

I think the advantage of it is that it offers free transactions rather than other cryptocurrency and that makes it one of a kind.

Here some advantage of IOTA:
Iota offers the so-called Tangle instead of the Blockchain.
There is no mining. The number of Iotas is limited.
The transaction volume is infinitely scalable and there are no transaction fees.

IOTA stands for Internet of Things Application, and it’s a new crypto technology that facilitates transactions between devices on the Internet of Things (IoT). IOTA addresses the transaction fees and scalability issues of blockchain technologies by getting rid of the block and chain. Instead, in order to submit a transaction to the IOTA ledger, you must verify two other previous transactions.

This method of verification means there’s no central ledger, and there’s no need for miners to power the network.

IOTA is one of the first platforms to marry IoT and cryptographic payment processing, but that doesn’t guarantee that it will be successful. The market potential is huge, but ultimately the investment potential of IOTA comes down to implementation and adoption.

Steem is a cryptocurrency that was released in 2016. It can be traded on the open market through cryptocurrency exchanges and obtained in exchange for goods or services. The price is very volatile due to the limited amount that's available on the markets. It's not very liquid and relatively small trades can move the price. Steemit does allows for mining, even though it’s not the primary way to earn money. Units can be bought or sold against other cryptocurrencies.

STEEM is a brilliant innovation wherein social-media users are rewarded with STEEM tokens for actively participating in  steemit. Liking, Commenting and Writing quality content apparently earns you steem dollars.

I really don't have any idea what zcash is. I want someon to answer my question.

The purpose of ZCASH which helps provide enhanced privacy and verify transactions without knowing the identity of transaction makers or the amount being transferred.

From its features and the pace with which it trends on the market, do you think waves have any extraordinary feature making it unique?

Waves has become popular as it allows the creation of new cryptocurrencies on its platform. This can be used to create many self-sustaining ecosystems, as well as reward systems.

Waves are the name of the both, a proof of stake blockchain and the cryptocurrency that fuels that blockchain.

Waves enable you to make custom tokens, which means you can launch your own cryptocurrencies. You can also decentralize trading and crowdfunding, as it has integrated fiat currency gateways like USD/EUR/CNY right in your wallet.

Via Waves, you can also launch ICOs to fund your projects from around the world in a matter of minutes, without going through intensive cryptocurrency coding. This will make life easier for startups and open up a new era of community-backed projects.

The Waves cryptocurrency (WAVES) has real-world tradable value on various exchanges.

Waves is an open blockchain platform designed for ease of use and mass adoption. Anyone can use Waves to launch, distribute and trade their own crypto token. The platform is fully decentralized, transparent and auditable.

How you will compare the NEM vs ETH?

One major difference between the two platforms is how they handle smart contracts. Ethereum has smart contract functions coded right into the blockchain, whereas NEM doesn't have a concept of a “smart contract”. They expect applications to hold the functions necessary to manage the token logic, and only have the ledger managed by NEM