This tutorial offered by W3Schools provides a detailed explanation of Matplotlib: a comprehensive library for creating static, animated, and interactive visualisations in Python. Created by John D. Hunter, Matplotlib is an open source, low level graph plotting library which uses Python programming language.

The free tutorial is broken down into the following modules: 

• Matplotlib Get Started
• Matplotlib Pyplot
• Matplotlib Plotting
• Matplotlib Markers
• Matplotlib Line
• Matplotlib Labels
• Matplotlib Grid
• Matplotlib Subplot
• Matplotlib Scatter
• Matplotlib Bars
• Matplotlib Histograms
• Matplotlib Pie Charts

This is one of the many tutorials offered by W3Schools. W3Schools is an educational website which offers free online courses on coding, with the aim to make web development easy to understand and accessible to everyone. For more information, visit their official website.