Meaning:
“知识” means “knowledge,” and “付费”means “to pay for.” Nowadays, Chinese people are willing to pay for quality content online, and many subscribe to online courses or pay to have specific questions answered. This trend is known as “paying for knowledge online.” Websites like zhihu.com and fd.zaih.com are platforms where people can get their questions answered, sometimes free and sometimes with a small sum paid.
Example:
A: 暑假你有什么计划？
Shǔjià nǐ yǒu shénme jìhuà？
What’s your plan for summer vacation?
B: 我打算报一个网课学围棋。
Wǒ dǎsuàn bào yīgè wǎngkè xué wéiqí。
I plan to pay for an online course to learn to play go.
A: 知识付费现在很热门，好像我认识的人都上过网课。
Zhīshi fùfèi xiànzài hěn rèmén，hǎoxiàng wǒ rènshí de rén dōu shàngguò wǎngkè。
Paying for knowledge online is popular these days. It seems that all the people I know have taken online courses.