This is a proverb, which says that it is better to teach people what they already know than to teach them how to learn knowledge. The first "fish" is a noun, which refers to the existing knowledge, and the second "fish" is a noun, which refers to the method of fishing and the method of learning knowledge.
The reason is actually very simple. Fish is the purpose of doing things, and fishing is the means of doing things. A fish can solve temporary hunger, but it can't solve long-term hunger. If you want to have fish to eat forever, you must really learn how to fish.
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On June 20 15 16, the General Secretary attended the 2015 High-level Forum on Poverty Reduction and Development and delivered a keynote speech. He quoted "it is better to teach people to fish than to teach people to fish" and pointed out that helping the poor and giving them a good education is an important task of poverty alleviation and development, and it is also an important way to block the intergenerational transmission of poverty.