Where to read about more of hm2_7i95.0.stepgen.00.counts

I see the pins information in Hal Configuration window. My hm2_7i95.0.stepgen.00.counts fluctuations from -5 to 5. I don't know what does it mean! This is the similar case with other pins too, I don't understand their meaning. So, I would like to read more about those pins definition.

Where to read for pin /signal/parameters definition?

You need to do some reading, start with docs in this link
linuxcnc.org/docs/2.8/html/
Next link 7i95 user manual
www.mesanet.com/pdf/parallel/7i95man.pdf
and this link is pcconfig wizard, I recommend you load the program and practice setting up 7i95
linuxcnc.org/docs/2.8/html/config/pncconf.html

At beginning learning LCNC seem difficult. However, if you persist in short time you will be able to configure basic system. Like everything else in life, practice and persistence makes you perfect.

man hostmot2

Also if you have a oscillation in these numbers when not moving
it indicates a tuning issue (probably the PID's P set too high)