What are the best free subject-learning blogs for practice problems and beginner-friendly explanations?

Here are some of the best free subject-learning blogs / sites for beginner-friendly explanations and practice problems, grouped by subject.

Math

• Khan Academy — excellent step-by-step explanations and lots of practice.
• Paul’s Online Math Notes — especially good for algebra, calculus, and differential equations.
• Math Is Fun — very beginner-friendly and easy to browse.
• Art of Problem Solving (AoPS) Community / Blog — great for more challenging math practice, especially contest math.

Science

• CK-12 — free science and math explanations with practice questions.
• Physics Classroom — strong for beginner physics concepts and problems.
• A Level Physics Online — clear explanations and practice for physics topics.
• Chemguide — very useful for chemistry concepts explained simply.

Computer Science / Programming

• GeeksforGeeks — huge number of beginner explanations and coding practice problems.
• freeCodeCamp Blog — beginner-friendly tutorials and learning paths.
• OverTheWire wargames — practice-based learning for Linux and security fundamentals.
• The Odin Project — very good for web development with hands-on projects.

Statistics / Data

• Seeing Theory — visual and beginner-friendly statistics explanations.
• Stat Trek — simple stats tutorials with examples and practice.
• Towards Data Science — many beginner articles, though quality varies by author.

Economics / Finance

• Aptitude / exam-prep blogs often have practice questions, but quality varies.
• Marginal Revolution University — clear explanations of economics basics.
• Investopedia — not a blog in the strictest sense, but very beginner-friendly for finance/econ definitions and examples.

Languages / Writing

• BBC Learning English — great beginner explanations and exercises.
• Duolingo Blog / WordReference forums — useful for language practice and explanations.
• Purdue OWL — excellent for writing, grammar, and citation basics.

Best all-around picks

If you want just a few to start with:

1. Khan Academy
2. CK-12
3. freeCodeCamp
4. Paul’s Online Math Notes
5. Physics Classroom

If you want, I can also give you:

• a subject-by-subject list for your exact class level,
• blogs with lots of practice questions only, or
• a best free resources list for one subject like math, physics, biology, or programming.