Asset collection interval defines how often the catalogue service polls to see if new assets have been added to the repository. When set to 5 minutes, it may take 5 minutes before a newly uploaded asset appears in te catalogue. Setting the interval to lower value will increase the load on the server.
Transcoding interval does something similar but now for picking up transcoding jobs. Setting a lower value will increase the load on the server.
The Clean-up section defines when assets (including schedules) are removed from catalogue or file system.
Orphaned assets are for example abandoned file upload actions.