I have a solaris e250 box where the root partition have becom full. I need to recover space but when I delete files using rm the space they take up is still in use. As you can guess I am very new to Solaris. I guess that the system has a method to hold onto deleted files to allow for recovery. I have also noticed in the var/adm dir some very large log files can I delete these.

Its been a long time since I saw that but as I recall the problem was due to an application still referencing the a file (like a log file). If you looked at space with the df -k command, then df is gets the file system space calculation from the file system inode table. So if the application still has that file open, then inode still has the space allocated in the kernel. You either need to stop the application or reboot the machine to make df report correctly. This is my best guess. By the way, if your new to unix you may want to get in the habit of using "rm -i " just to be on the safe side.
Paul