Raise your hand if you know what metadata is.

I think everyone's heard of data. For the purposes of this column, data refer to files on your hard drive such as music, video, photos and even office documents.

It's easy to find data based on the file name, but what if you don't remember the exact file name?

That's when metadata can come to the rescue.

Metadata is "data about your data."

The metadata about a song file on your hard drive might include the title, artist, song length and even album artwork.

If you've ever used iTunes to rip songs off one of your CDs, chances are iTunes accessed an Internet database to retrieve information about each track. That information is metadata, and it's invisibly inserted into the song file.

When it's time to play that song, the metadata helps you find the right file. You might have the song "Fire" by both Bruce Springsteen and the Pointer Sisters, and it's metadata that allows you to play the one you want.

If you own a digital camera and organize your photos on your computer, you're using metadata as well.

As each picture is captured, a digital camera records information such as shutter speed, f-stop and a time and date stamp for each file.

Where metadata really gets interesting is when you add your own.

Although iPhoto can figure out what day you shot your photos, it can't identify the event or names of people in the picture. By manually entering this information for each photo, you make it easier to search for the photo later.

Photo organization programs allow the user to add keywords or descriptions to each image.

If you enter accurate metadata about your photos, putting together a family album will be much easier. Looking through thousands of photos for the three pictures of Aunt Margaret will seem like an eternity compared to entering her name in the iPhoto search field and pressing "return."

ITunes can learn the name and artist in your song files, but only you can tell it what your favorite songs are.

It has a handy feature to allow the user to assign a 1- to 5-star rating for each song. If you rate your favorite songs, creating a playlist of your 4- and 5-star songs will take only a few seconds.

So this week's lesson is to enter metadata for your songs and photos.

As the years go by and we acquire more and more data, searching for the exact file we need isn't going to get easier unless we lay the foundation from the beginning.

Jim Rossman is technical manager for Macintosh support for A.H. Belo Corporation.