7.11. Searching for Photos by Text
The keyword mechanism described above is an adequate way to tag photos with textual descriptions. But as you know by now, there are other ways. The name you give a picture might be significant; its original file name on the hard drive might be important; and maybe you've typed some important clues into its Comments box or given its film roll an important name .
Anyhow, that's the purpose of the Search box in the lower-right corner of the iPhoto window.