35. What is Docker? What it can be used to?

Docker is a containerization platform that enables the creation, deployment, and running of applications in isolated environments called containers. Containers include all the necessary components to run an application, such as code, libraries, and dependencies.

Advantages of Docker:

1. Isolation: Containers run in isolated environments, preventing dependency conflicts and making application management easier.
2. Portability: Containers can run on any machine with Docker, regardless of the operating system, making it easier to move applications between different environments.
3. Performance: Containers are lightweight and start up faster than traditional virtual machines, allowing for more efficient use of resources.
4. Ease of scaling: Docker simplifies scaling applications by allowing easy creation and management of multiple container instances.
5. Environment consistency: Docker ensures that applications run in identical environments on both developers' machines and production servers.

Example Dockerfile:

# Use base image
FROM node:14

# Set working directory
WORKDIR /app

# Copy application files
COPY package*.json ./
COPY . .

# Install dependencies
RUN npm install

# Run the application
CMD ["node", "index.js"]

Example of running a container:

# Build Docker image
docker build -t my-node-app .

# Run container
docker run -p 3000:3000 my-node-app

Docker is a powerful tool that significantly simplifies application management and deployment across different environments.