Does the full backup truncate transaction log?

Does the transaction log get truncated when I take a full backup using command

BACKUP DATABASE AdventureWorks
    TO Adventurewks
GO

Or do I have to take a log backup separately?

BACKUP LOG AdventureWorks
   TO Adventurewks;
GO

Or is the log backup just for a point-in-time restore?

From serverfault hyty

• A log backup is needed to truncate the logs.

  Here is an article that contains some information on this, http://technet.microsoft.com/en-us/library/ms186865.aspx

  From Grishanko