system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly is Critical Thinking?

I always notice a lot of the “ critical thinking “ skill mentioned in articles and even some books that I read, I got interested and googled it but still didn’t get the information I needed to understand why it’s so important skill. But then after a while I got a friend who is exceptionally different in the way that he communicates information and how he asks questions, it is so fascinating for me cuz it’s all practical and crucial knowledge. I always find my self following his decisions. I think it’s something that’s related to critical thinking skills, and if it’s true I wonder what someone like me has to go through to master this skill.
gpt
It starts fairly simple, then there are some more difficult skills to develop. It isn't a "talent". It takes practice. At the simplest level critical thinking is about questioning and not simply accepting conclusions as valid without understanding the premise and assumptions. Common mistakes are using narrow examples and extrapolating them as representative for larger populations. 

First step is to develop some basic logic. For example:

All dogs have four legs. That animal has four legs. Therefore it is a dog.

All dogs have four legs. That animal is a dog. Therefore it has four legs.

One of the above is incorrect logic. These are the fairly straightforward logical errors. 

Then you start to develop the ability to break down arguments and assertions to figure out underlying assumptions and then ask or research whether and under what conditions would those assumptions be valid. 

The more difficult areas usually surround our own or built in biases. These can be hard to see. This is why critical thinking requires the ability to view issues from different perspectives - "why would this be true for this group/individual".

At some point, understanding some fundamental concepts like Baye's Theorem really brings home how "intuition" can mislead. It is good to have a grounding on basic probability and statistics. It doesn't have to be deep but many/most scientific research use some kind of statistical framework. (it is very easy to get this wrong because the words used in language are seldom precise and can be manipulated/misunderstood)

Then there is the ability to reason backwards. Most people reason forward but a very powerful technique is to do the reverse. 

There is also some value in understanding "cognitive breakdowns". Why framing, regret aversion etc lead to failures in reasoning. This gives you some idea how issues can be somewhat manipulatively presented - ie disguising an agenda with seemingly objective numbers/facts. Once you get to this point, it is probably safe to say that your critical thinking skills would be better than 99.9% of the population.