TimeXY
IRI MP RESEARCH ATMOSPHERE GLOBAL CAM5 amvSST amv_hist_neg.D Daily[QBOT VBOT PRECC V200 PSL V850 PRECL U850 TBOT FLNS T850 SHFLX FSNS FLNT Q200 LHFLX Z850 Z500 Z200 U200 UBOT Q850 T200 ]
IRI MP RESEARCH ATMOSPHERE GLOBAL CAM5 amvSST amv_hist_neg.D Daily Z500[ X Y | Time]MMM
This list of Active Objects appears in Expert Mode and are all the datasets that you currently have open. The last one (IRI MP RESEARCH ATMOSPHERE GLOBAL CAM5 amvSST amv_hist_neg.D Daily Z500) is the one you are currently working with.

means the grid is missing
Mmeans the grids match
Omeans the grids are offset
Smeans the grids could match by sampling
Dmeans the grids differ
Grid Comparisons
When you have multiple variables active, a table of grid comparisons appears to the right. These comparisons are between the last variable and all the others (so the last row always has matches or blanks).

IRI MP RESEARCH ATMOSPHERE GLOBAL CAM5 amvSST amv_hist_neg.D Daily Z500 options

You have a number of options for working with this data set. You can also modify the dataset by You can also get the dataset output as

Dataset Documentation

We start with a quick reminder of where you are in the collection of datasets.
...RESEARCHATMOSPHEREGLOBALCAM5amvSSTamv_hist_neg.DDailyZ500

As you go from left to right, the datasets listed get more and more specific, ending with the current dependent variable, IRI MP RESEARCH ATMOSPHERE GLOBAL CAM5 amvSST amv_hist_neg.D Daily Z500. Datasets with documentation are marked (*): the * links to the documentation directly.

Grids

Grids are the independent variables, i.e. what the current dependent variable (Z500) depends on.
Time
grid: /Time (days since 1930-01-01 12:00:00) ordered (1 Jan 1929) to (31 Dec 2014) by 1.0 N= 31411 pts :grid
Longitude
grid: /X (degree_east) periodic (0) to (2.8125W) by 2.8125 N= 128 pts :grid
Latitude
grid: /Y (degree_north) ordered [ (87.86S) (85.1S) (82.31S) (79.53S) (76.74S) (73.95S) (71.16S) (68.37S) (65.58S) (62.79S) (60S) (57.21S) (54.42S) (51.63S) (48.84S) (46.04S) (43.25S) (40.46S) (37.67S) (34.88S) (32.09S) (29.3S) (26.51S) (23.72S) (20.93S) (18.14S) (15.35S) (12.56S) (9.77S) (6.98S) (4.19S) (1.4S) (1.4N) (4.19N) (6.98N) (9.77N) (12.56N) (15.35N) (18.14N) (20.93N) (23.72N) (26.51N) (29.3N) (32.09N) (34.88N) (37.67N) (40.46N) (43.25N) (46.04N) (48.84N) (51.63N) (54.42N) (57.21N) (60N) (62.79N) (65.58N) (68.37N) (71.16N) (73.95N) (76.74N) (79.53N) (82.31N) (85.1N) (87.86N)] :grid

Other Info

These are additional attributes, some of which can be used to change how the data is processed or displayed.
datatype
realarraytype
FieldType
104
MemoryOrder
XY
missing_value
9.96920997E36
pointwidth
0
units
m
standard units*
meter