The Findutils package contains the find, locate, updatedb and xargs programs.
The find program searches for files in a directory hierarchy which match a certain criteria. If no criteria is given, it lists all files in the current directory and it's subdirectories.
Locate scans a database which contain all files and directories on a filesystem. This program lists the files and directories in this database matching a certain criteria. If a user is looking for a file this program will scan the database and tell him exactly where the files he requested are located. This only makes sense if the locate database is fairly up-to-date else it will provide out-of-date information.
The updatedb program updates the locate database. It scans the entire file system (including other file system that are currently mounted unless it is told not to do so) and puts every directory and file it finds into the database that's used by the locate program which retrieves this information. It's a good practice to update this database once a day to have it up-to-date whenever it is needed.
The xargs command applies a command to a list of files. If there is a need to perform the same command on multiple files, a file can be created that contains all these files (one per line) and use xargs to perform that command on the list.