What is data extraction in SAP BW?

What is data extraction, and what are the delta types/update methods? What type of extractors use which type of delta methods, along with tables and fields which are being used by extractors for that particular extraction?

Data extraction in BW is extracting data from various tables in the R/3 systems or BW systems. There are standard delta extraction methods available for master data and transaction data. You can also build them with the help of transaction codes provided by SAP. The standard delta extraction for master data is using change pointer tables in R/3. For transaction data, delta extraction can be using LIS structures or LO cockpit.