"...and so on" is similar in meaning to "etc." ("et cetera"). It means that there are more things that you could add to a list, but you're not going to say all of them.
In this example:
Heavy drinking can lead to liver damage and so on.
... the speaker means that drinking can lead to liver damage as well as other health problems.
"...and so on" is more casual than "etc." or "et cetera". It's better for spoken English.