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 you're looking for a file this program will scan the database and tell you exactly where the files you requested are located. This only makes sense if your locate database is fairly up-to-date else it will provide you with out-of-date information.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 you specify it not to) 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 so that you are ensured of a database that is up-to-date.
The xargs command applies a command to a list of files. If you need to perform the same command on multiple files, you can create a file that contains all these files (one per line) and use xargs to perform that command on the list.