When to use Motion and when to use halui

I am confused by two examples with which I have been working, and I referred to them in another posting
MPG Handwheel - how to make it operate when linuxCNC/axis not homed

In the code wiki.linuxcnc.org/cgi-bin/wiki.pl?Hooking_Up_A_MPG_Pendant jogging is carried out using what I understand is Motion in such hal as net pend-counts axis.0.jog-counts <= encoder.0.counts

but the code for using a Joypad at wiki.linuxcnc.org/cgi-bin/wiki.pl?Simple_Remote_Pendant
action is via halui in lines such as
net jog-x-analog <= mux2_x.out => mux2_x.in0 halui.joint.0.analog halui.axis.x.analogWhy does one use motion, the other halui. 

The joypad is not real time as its connected by USB.
The MPG uses an encoder so its real time
halui is a userspace non real time component
Motion is real time

expand man pages on the docs page will list the user space components followed by the real time components

So is halui an interface between userspace and kernel/real-time?

I am a little unclear as to what you mean by "expand man pages on the docs page".
A url would help this ignoramus.