The bulk logs are extended version of your results file. 

Typically the log file include:

ID: of the bulk upload.

Message_id: the message identification number.

Sku: The sku has been modified

Operation: That field contains what request has been sent to our system

Type: That header will define the nature of the update of that item. Example  Inventory(stock), Images(media), Relations(shippng)

Date: Timestamp of the action

Result: The result of that action 

Messages: Typically that header will give you value only if the Results are (failure/error)

Example log sheet: