hlp filters

Hello Everyone;
What is the tracking filter? What are applications of it? Please explain. Please introduce me any paper/ebook/article/...

tracking filters are those filters which tracks the training given to them and then reshaping the data in order to remove the noise and intersymbol interference.
you may refer the book
digital communication by proakis

the most famous type of tracking filters are "kalman" filters you can find many useful things in google search