Understanding QoS

Can someone expalin what this QoS map tables mean.  Is it important to understand what they mean or are they auto generated by just turning QoS on on the switch/router.  How do you read them? What do the d1 and d2 represent?  I thought DSCP valuse range from 0 - 63.  If that's the case, on the DSCP-COS map whay are the numbers onlt going from 0-7.  I can understand why the Cos-dscp map make sense since the numbers from 0 - 56 are represented in the DSCP values.  It confusing how the maping values change on

1.
Dscp-cos map:
     d1 :  d2 0  1  2  3  4  5  6  7  8  9
     ---------------------------------------
      0 :    00 00 00 00 00 00 00 00 01 01
      1 :    01 01 01 01 01 01 02 02 02 02
      2 :    02 02 02 02 03 03 03 03 03 03
      3 :    03 03 04 04 04 04 04 04 04 04
      4 :    05 05 05 05 05 05 05 05 06 06
      5 :    06 06 06 06 06 06 07 07 07 07
      6 :    07 07 07 07

2.
Dscp-switch priority map:
     d1 :  d2 0  1  2  3  4  5  6  7  8  9
     ---------------------------------------
      0 :    00 00 00 00 00 00 00 00 00 00
      1 :    00 00 00 00 00 00 01 01 01 01
      2 :    01 01 01 01 01 01 01 01 01 01
      3 :    01 01 02 02 02 02 02 02 02 02
      4 :    02 02 02 02 02 02 02 02 03 03
      5 :    03 03 03 03 03 03 03 03 03 03
      6 :    03 03 03 03
3.
scp-dscp mutation map:
   Default DSCP Mutation Map:
     d1 :  d2 0  1  2  3  4  5  6  7  8  9
     ---------------------------------------
      0 :    00 01 02 03 04 05 06 07 08 09
      1 :    10 11 12 13 14 15 16 17 18 19
      2 :    20 21 22 23 24 25 26 27 28 29
      3 :    30 31 32 33 34 35 36 37 38 39
      4 :    40 41 42 43 44 45 46 47 48 49
      5 :    50 51 52 53 54 55 56 57 58 59
      6 :    60 61 62 63

I have all the notes that I can read, but none expalins how to read these and why they change like that.  This subject is kicking me in the gut.  Help.!!!..  -:)

The terms ingress and egress are confusing as well

for example, when I run the command
 # sh mls qos interface statistics

I get this---

GigabitEthernet0/2
Ingress
  dscp: incoming         no_change     classified policed    dropped (in bytes)
Others: 2005512940  1999692272   5820668                   0          0        
Egress
  dscp: incoming       no_change     classified policed    dropped (in bytes)
Others: 3781506923    n/a              n/a                                  0          0        

Why on Egress there  is ingress, I can understand Ingress and Incoming

Explain the ingress and egress on the same port especially when you have to assign DSCP or CoS values

Can someone help.  Like I mentioned, none of the books or white papers explain.  They just dive into the details of QoS.  IIt's difficult to move forward before I understand these basics and hoping someone cn help.