Can you explain what Docker containers are and how they work?

Docker is a platform for building, shipping, and running applications in isolated containers. Containers allow you to package an application with all its dependencies into a single image that can run on any system with Docker without conflicts.

Containers operate at the operating system level, using isolation features (namespaces, cgroups), making them lighter and faster than virtual machines. They are launched from images described in a Dockerfile.

Example Dockerfile for a simple Python application:

FROM python:3.9-slim
WORKDIR /app
COPY . /app
RUN pip install -r requirements.txt
CMD ["python", "app.py"]

This container guarantees that the application will work the same way in any environment.