Yagyavalka rishi when leaving the home for sanyas gave the knowledge of souls to his wife maitreyi therefore this soul gyan is called maitreyi gyan .

In fact vedas contain the whole knowledge of karm gyan and upasana and therefore they do not insist much on knowing about the universe forming or the brahman and leave it to science .

ko addhā veda ka iha pra vocat kuta ājātā kuta iyaṃvisṛṣṭiḥ |
arvāgh devā asya visarjanenāthā ko veda yataābabhūva ||
iyaṃ visṛṣṭiryata ābabhūva yadi vā dadhe yadi vā na |
yo asyādhyakṣaḥ parame vyoman so aṅgha veda yadi vā naveda ||6,7/129/10mndlm rigveda

Who verily knows and who can here declare it, whence it was born and whence comes this creation?
The Gods are later than this world's production. Who knows then whence it first came into being?
 He, the first origin of this creation, whether he formed it all or did not form it,
Whose eye controls this world in highest heaven, he verily knows it, or perhaps he knows not.

Maitreyi gyan tells the relation of soul to soul eg. A  wife soul to a husband soul and similarly for other relations too .

This whole world is governed by souls and stronger souls take the refuge on weaker souls and thus the person acts accordingly .

There is a strong and long duration of relation in wife and husband souls therefore it is said to be continued to 7 births .

Coming to right or wrong births depend upon the deeds performed during previous birth therefore human life is said to be one and only one deciding  life for betterment .

Souls  in environment can be contacted  and called by a human soul  under maitreyi gyan .