Vedavyāsa compiled all the Vedic literatures. There are millions of verses in the Purāṇas, Mahābhārata, in Śrīmad-Bhāgavatam. Śrīmad-Bhāgavatam itself contains 18,000 verses. Mahābhārata contains about more than 100,000’s of verses. Similarly, there are other Purāṇas, Upaniṣads, etc. He is the editor and compiler of all these Vedic literatures.
He summarized all the Vedic knowledge in sūtra. Sūtra means codes. Just like there are business codes, Bentley’s codes, Henry’s codes. So one or two words will give impression of volumes of knowledge. Businessmen, they need it to save the expenditure on wiring, on telegraphing. Just like CIF. “Accept your offering. CIF.” CIF means “cost including freight.” That means goods will be delivered at your door. So similarly, there are many codes in business matter. In military arts there are so many codes. So Vedānta-sūtra means codes of all Vedic knowledge.
Just like athāto brahma jijñāsā. Atha, “now,” ataḥ, “after this,” brahma, “the Supreme Absolute Truth,” jijñāsā, “one should inquire.” This can be explained in volumes of books athāto brahma jijñāsā.
Ref >> Srila Prabhupada Vani.