Beginner asking for explanation of escape character

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http://www.linuxforums.org – Hi, I just am make friend with scripting 2 weeks ago and has completely no idea how to search for the keyword to all the following syntax. Please help. var1="${mode:-AUTO}" Does this mean that the variable var1 is assigned with the pass-in argument? Then what does ':-AUTO' means? var2="${mydate}_lock.text" var3="$DTA/mypath/.runLock" Asuming that mydate is 20091223, I understand that var2=20091223_lock.text, but how about var3? Why is no "{" after the "$". Also, I don't seem to find a directory of DTA/mypath. Is $DTA a keyword? awk -vediauto="$EDIAUTO" -vedimanual="$EDIMANUAL" \ -vuser="$USER" --source ' I can't find the declaration of vediauto, vedimanual or vuser. I also don't find them as keyword of awk on any website. So, may I know what are the meaning of the 3 words: vediauto, vedimanual or vuser. Also, I only find a apostsophy " ' " in the statement. All the above works in the program miraclely... Can you please help to advise the meaning behind them. And I would appreciate if you can advise me how to search for help of the above code in the web. I am not sure what is the keyword I should look for when googling. Thanks in advance. Regards Te (HowTos)