I must beg to differ slightly with the earlier replies.
Inbound and Outbound can be seen as page specific, while Internal and External are site specific.
Inbound links - Links that can bring a user to a page.
Outbound links - Links that can lead a user off a page.
Internal Links - Links between pages on the same site.
External Links - Links related to outside sites.
All of that being said, unless otherwise specified, "inbound links" are generally referring to inbound links from external sites, and "outbound links" are most often describing links to external sites.
edited for grammar and clarity
[edited by: Macguru at 3:09 pm (utc) on Dec. 17, 2002]