childhood; when one was a child
Refers to the time of one's childhood; often used adverbially as 'in my/one's childhood' or as a noun phrase.
I often played in this park when I was a child.
He talked about his childhood memories.
幼少期 is a formal, literary term for early childhood, whereas 子供の頃 is the everyday, conversational way to say 'in my childhood'.
Compound of 子供 (child) + の (possessive particle) + 頃 (time, about). A straightforward phrase meaning 'the time of being a child'.