What is the function of twain, wia, sdk in visual studio? Then i have a printer cannon pixma mp198 is it support twain or wia?

Disclaimer: I am not a VB.NET programmer nor do I have any experience with TWAIN or WIA.

Twain vs WIA

TL;DR: Twain is better for scanners and requires a vendor dialog, WIA for cameras with a standard dialog.

Your printer/scanner can do both.

Here're some useful links I found for VB.NET.