“Alchemy is a Web3 developer platform focused on making blockchain development easy.”
What they basically do is that they provide you, and the people part of your team, a node. This Node help you to be a part of the Web3 blockchain of the different currencies that this application website as to offer. There is some example of other Web3 companies that are a part of this “community”:
What Is a Node and What Does it Do?
The Google defines a Node like "a point at which lines or pathways intersect or branch; a central or connecting point; the intersections of two or more such arteries would clearly become major nodes of traffic and urban activity".
But let's start from the basics! A node is essentially a program running on a single computer that allows you to connect with the rest of the blockchain network. It connects with other nodes to send information back and forth, checks that transactions sent between people are valid, and stores important information about the state of the blockchain.
In particular, one of the peculiarities of a blockchain network is that the network is essentially composed of only nodes: that is, the physical hardware running a blockchain such as Ethereum or Bitcoin is just the collection of all the nodes around the world being run by individual people. There's no master server or single source of truth - that's why it's decentralized!
Finally, it's important to note that there's no way to access the information on a blockchain without using a node. Can't be done. Think of it like the browser for the blockchain.
What Is Metamask?
MetaMask is a free web and mobile crypto wallet that allows users to store and swap cryptocurrencies, interact with the Ethereum blockchain ecosystem, and host a growing array of decentralized applications.
The good thing with MetaMask is that it allows users to fully interact with Ethereum without downloading the entire blockchain. Indeed, you can even run an Ethereum DApp without using a full Ethereum node. The wallet was created in 2016 by Aaron Davis and Dan Finlay.