GATK BaseRecalibration report

hi everyone I use GATK to do snp call. But I don't understand the BaseRecalibration report as follows . And i really don't known the word 'Observations' 'Errors' stand for. Thanks in advance RaedGroup            R11               R11               R11 EventType            M                  I                 D EmpiricalQuality     15.0              28.0               26.0 EstimatedQReported    32               45                  45 Observations         1.23e+08     1.23e+08               1.23e+08    Errors            4.35e+06      2.15E+05             4.28e+05      ...