What is data mapping and data modelling?

Data mapping deals with the transformation of the extracted data at FIELD level i.e. the transformation of the source field to target field is specified by the mapping defined on the target field. The data mapping is specified during the cleansing of the data to be loaded.

For Example:
string(35) name = “Siva Krishna “;
string(“01?) nm=NULL(“”);/*(maximum length is string(35))*/
Then we can have a mapping like:
Straight move.Trim the leading or trailing spaces.
The above mapping specifies the transformation of the field nm