Grammar Handbook and/or Reference Book

Do you have a go to grammar handbook and/or reference book to answer those quick questions that come up?

When the student is not asking for an in depth answers just the “why?” questions that always come up

“mom, why does a comma need to go there?” “Why is there a colon there?” “Why is there a dash there?”

My oldest is in 3rd grade and when doing copy work or reading she will ask. Sometimes I know, but sometimes I draw a blank. I know it is correct because it looks correct, but the exact reason I might not be sure or I am not sure how to explain it correctly.

I thought a few weeks ago there was a post about handbook/reference books for grammar, but I can’t find it now. Thanks!