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In last section we tried to answer the question of why use Docker and we eventually said that we use

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Docker because it makes it really easy to install and run a new software on our computer.

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We're not going to try to answer the other big question here which is what is Docker.

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Well this question is a lot more challenging to answer.

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Anytime you see someone refer to Docker in a blog post or an article or a forum or wherever it might

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be they're kind of making reference to an entire ecosystem of different projects tools and pieces of

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software.

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So if someone says Oh yeah I use Docker on my project they might be referring to Docker client or Docker

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server they might be referring to Docker Hub or Docker compose.

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Again these are all projects tools pieces of software that come together to form a platform where ecosystem

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around creating and running something called containers.

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And so your immediate question might be.

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OK well what's a container.

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That's a good question and that's a question that we're going to be trying to answer throughout this

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entire course.

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Just a moment ago when I ran that command at my terminal of Docker run read this and went through a

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little series of actions behind the scenes we're going to examine that entire series of actions very

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closely over time.

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But right now let me give you two important pieces of terminology.

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When I ran that command something called the docker S.L. I reached out to something called the Docker

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Hub and it downloaded a single file called an image an image is a single file containing all the dependencies

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and all the configuration required to run a very specific program for example this which is what the

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image that I just downloaded was supposed to run.

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This is a single file that gets stored on your hard drive and at some point time you can use this image

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to create something called a container a container is an instance of an image and you can kind of think

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of it as being like a running program.

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We're going to go into great detail over time over behind her to learn exactly how a container works

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exactly.

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But right now all we really need to understand is that a container is a program with its own isolated

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set of hardware resources so it kind of has its own little set or its own little space of memory has

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its own little space of networking technology and its own little space of hard drive space as well.

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OK so I didn't really answer the question here of what Docker is but we did learn at least that a reference

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to Docker is really talking about a whole collection of different projects and tools.

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And we also picked up two important pieces of terminology a darker image and a container.

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Now these images and containers are the absolute backbone of what you and I are going to be working

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with throughout the rest of this course.

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So let's take a quick pause right now.

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We're gonna come back the next section.

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We're going to start talking a little bit more about how we work with images and containers.

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So quick break and I'll see you in just a minute.