Indexing in Laserfiche is managed and performed by the Laserfiche Full-Text Search and Indexing Service. You can find more information regarding how that works here.

For your second question, when you delete/purge an entry in Laserfiche, the system doesn’t delete it from the disk immediately. Instead the file is moved to a queue of files that are deleted in the background. This activity that you are seeing is indicating that the background operation is currently running. In short, it’s deleting volume files that were marked for deletion.