This word can be used for a boy of any age, but it is particularly common for younger boys.
Here are some other ways to say "little boy" in Portuguese, depending on the context:
* "menino pequeno" (literally "small boy")
* "criança" (child)
* "rapazinho" (a more informal and endearing term, similar to "little guy")
* "garoto" (boy)
The specific term you choose will depend on the age of the boy and the tone you want to convey.