Recycled data is a very interesting concept within your transaction log that most people don't realize is there.  It is very similar to the way deleting a file works on an operating system.  When you delete a file, you don't physically remove all traces of that file from your file system.  You simply remove a bit in the header of the file that tells the OS it is a valid file.  The data still exists on your disk drive until something overwrites it.  The same concept occurs internal to the transaction log.  When you issue a transaction log backup, the committed transactions are "removed" from the transaction log.  This is NOT a physical removal of that data.  There is simply an update to a bitmap that tells SQL Server which entries in the transaction log are still valid.  When you are reading the raw transaction log as Log Explorer is doing, you will see this data present in the transaction log.  A transaction log writes in a circular manner.  When it reaches the end of the log, it will begin writing back to the pages at the beginning of the log if there is space available.  If not, it will allocate more space to the log.  The recycled data is that data which has been "removed" due to a transaction log, but has not yet been written over by SQL Server.  I generally do not look at recycled data.

Your transaction log contains entries for every conceivable operation that occurs in SQL Server.  I believe there are 47 different operations that are tracked.  you can filter the entries in your transaction log to isolate only specific operations.  You can also isolate this to user data only which is highly recommended since you shouldn't be playing with data in system tables.  One really nice thing about Log Explorer is the extensive help system that provides a significant amount of training.  If you don't understand what a particular operation code is, you can simply look it up in the help system.

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