Yashoda was the deity, who brought up Krishna, the son of Devaki and Vasudeva, a mythological king. The image of yashoda illustrates an incident of the birth of Krishna, some aspects.
According to a mythological story, Vasudeva had several wives, including Devaki and Rohini. After the marriage of Devaki, her brother (Kamsa) had a premonition that her eighth son would kill him. On the request of Vasudeva, Kamsa did not kill Devaki immediately. But, Kamsa proceeded to kill the first six of Devaki`s sons. When Devaki pregnant for the seventh time, Vishnu transferred the embryo to Rohini`s womb to prevent the child to get murdered by Kamsa and it was announced that Devaki had miscarried. When the child was born later, it was called Balarama, where a slightly different story of this incident was given in another text. Afterwards, Vishnu allowed Devaki to conceive him and the Goddess of Sleep and Night was conceived by Yashoda, the wife of the cowherd Nanda. Both Nandaraja and Yashoda used to look after Rohini in their country retreat.
Now, Vishnu was Devaki`s eighth son whom her brother Kamsa is confirmed to kill. But, Lord Vishnu managed the situation in such a way that that Devaki and Yashoda would give birth at the same time and Yashoda would forget the sex of her child. It happened as planned and on the night of the child`s birth, Vasudeva took his son and left him with Yashoda in exchange for her daughter whom he took back to Devaki.
In this way, Vishnu was born as Krishna and was brought up by Nanda and Yashoda in the safety of the country. On the other hand, Vasudeva and Devaki pretended that their eighth child was a daughter. Yashoda brought up Krishna thinking him to be her own child. But later, she became aware of the fact when Krishna became a young boy and had to leave for Mathura to kill Kamsa. But, she still adored Krishna like her own child