In short, "rational decision" is a decision based on a series of rational, workable and logical thinking. "Irrational" is to ignore "rational" decision-making, completely based on "subjective" and "perceptual", and made some things even one cannot understand one's behavior and decision.
In the financial market, we can often see a lot of such behavior. For example, when the stock market looks so "good", the general "irrational" investors will think: In a rising trend, any kind of stocks are sure to rise, if they do not buy the stock, there will be no chance in the future.
Hence, stocks were purchased only relied on personal feelings with absence of rational analysis of the company's performance, profitability, returns and investment risk or even not sure about its business nature. As a result, when stock market bubble burst, the stock on hand became waste paper and would be regretted as to why such "irrational" and "unwise" decisions were made.
A rational act must be considered carefully. Whether on investment or anything else, what should be considered beforehand? Think of five things:
1. Why - Why to do?
2. What - What to do?
3. How - How to do?
4. When - When to do?
5. Who - Who to do?
After the above consideration can perform less work with better results.
Therefore, "rationality" corresponds with the Dharma "Six Degrees" of "Wisdom".