Śrīmad-Bhāgavatam is the last contribution of Vyāsadeva. Śrīmad-Bhāgavatam, nigama-kalpa-taror galitaṁ phalaṁ idam (SB 1.1.3). In the beginning, introduction of Śrīmad-Bhāgavatam, Vyāsadeva giving the information that this Śrīmad-Bhāgavatam is the nigama-kalpa-taror galitaṁ phalaṁ idam. Nigama means Vedas. So he compared the Vedas as a tree where you can get many fruits. So this Śrīmad-Bhāgavatam is described as nigama-kalpa-taror galitaṁ phalaṁ idam. Kalpa-taru means desire tree. Desire tree, you can get any kind of fruit from that tree. In the material world there are many different types of trees, fruits and flowers, but you can get one type of fruit or one type of flower from a particular type of tree. But there is another tree; that is in the spiritual world. That is called desire tree. Whatever you want from that tree you can get. Kalpa-taru. The spiritual world, description of the spiritual world is there in the Brahma-saṁhitā. Cintāmaṇi-prakara-sadmasu kalpa-vṛkṣa (Bs. 5.29). There the trees are kalpa-vṛkṣa, or nigama-kalpa-taru. Kalpa-taru or kalpa-vṛkṣa, the same thing.
So Veda means knowledge. So from the Vedas you can get all kinds of knowledge, both material and spiritual. Therefore it is called Veda, knowledge. So in that tree of knowledge the ripened fruit is Śrīmad-Bhāgavatam. Śrīmad-Bhāgavatam is written by Vyāsadeva after writing four Vedas and the eighteen Purāṇas, the 108 Upaniṣads, then Vedānta-sūtra and Mahābhārata, in which Bhagavad-gītā is set up. So after compiling all these Vedic literatures Vyāsadeva was not satisfied. Then his spiritual master advised him to describe the activities of the Supreme Personality of Godhead. That is Śrīmad-Bhāgavatam. Bhagavāta. Bhagavān.