Hello, "Pass on" and "pass down" can mean the same thing, but "pass on" most likely will mean to share or pass something along with friends, random people, or the people surrounding you. For example "These stories will be passed on for many years to come." The stories could be passed on to friends, children, strangers, etc. When you say "pass down", it generally means to pass something along within a family. For example, "These traditions will be passed down to his children." It is restricted to the family, and will not be shared with everyone. While these are the most common occurrences for these phrases, they CAN be used to mean either one, and it is not exclusive to family or otherwise, it is just that this is the most likely situation for when the phrases are used. I hope this helped!

Generally, in 'pass down', the 'down' refers to generations (of people). So, you pass things down to your children, and your grandchildren. 'Pass on' doesn't have that specific meaning, so means 'pass it on to anyone'. Is that clear?