I guess the title says it all. There seems to be no obvious difference between directory traversal and file inclusion vulnerabilities.
But I guess there must be some difference, since the www.cvedetails.com use the following categorizations:
Bypass a restriction or similar Cross Site Scripting Denial of service Directory Traversal Execute arbitrary code on vulnerable system Gain Privileges Http Response Splitting Memory Corruption Obtain information Overflow vulnerability (includes stack and heap based overflows and other overflows) Cross site request forgery(CSRF) File Inclusion Sql Injection
Among these we can notice both directory traversal and file inclusion, so they must be different somehow.