what is the prioroty among ttrigger , workflow rule and approval process,which one would be executed first

i want to develop a function to upload bulk CSV data into profuct as below screenshot.

how to write the VF page and APEX code and how to deal with the csv file. i have no idea about the code develope.....

i want to develop a function to upload bulk CSV data into profuct as below screenshot.

how to write the VF page and APEX code and how to deal with the csv file. i have no idea about the code develope.....