What do the different fields in an annotation feature class mean?

Answer

The following are different fields in an annotation feature class and their meanings:

ObjectID
Unique identifier for each annotation feature.

Shape
The polygon shape that represents the outline of the annotation.

FeatureID
For feature-linked annotation, this field contains the ObjectID of the linked feature.

ZOrder
This field is unused at this time.

AnnotationClassID
The Annotation Class the annotation belongs to. For each annotation class there is one related symbol in the Symbol Collection that stores the symbology for that Annotation Class. You can edit the Annotation Classes in ArcCatalog by right-clicking the annotation feature class, selecting properties, and clicking the Annotation Classes tab.

Element
A 'BLOB' field that stores symbology and text geometry.

SymbolID
This is the ID of the symbol from the Symbol Collection for that annotation element. You can find the different symbols for the annotation feature class in the Symbol Collection listed on the Annotation tab of the annotation feature class properties in ArcCatalog. The ID number in this field corresponds with the number in parentheses in the Symbol Collection. A value of -1 in the annotation attribute table means that the symbol is stored inline and contains values that fall outside of the Symbol Collection's properties. Using symbols from the Symbol Collection allows one to quickly change annotation symbology when editing in ArcMap. It also improves the performance of the annotation because it optimizes annotation storage.

Status
Specifies the status of the annotation. 'Placed' or 'Unplaced'. 'Unplaced' annotation shows up in the 'Unplaced Annotation Window'.

TextString
The text for the Annotation.

Font Name
Specifies the name of the font.

Font Size
Specifies the font size in points.

Bold
Indicates if the font is bold.

Italic
Indicates if the font is italic.

Underline
Indicates if the font is underlined.

Vertical Alignment
Specifies the vertical alignment of the annotation: Top, Center, Baseline, or Bottom.

Horizontal Alignment
Specifies the horizontal alignment of the annotation: Left, Right, Center, or Full.

X Offset
Shifts the text position left or right.

Y Offset
Shifts the text position up or down.

Angle
Rotates the text angle counter clockwise (0 to 360 degrees), or clockwise (0 to -360 degrees).

Font Leading
Specifies the adjustment of regular spacing between lines.

Word Spacing
Specifies the percentage of spacing between words.

Character Width
Specifies the percentage of the font's character width.

Character Spacing
Specifies the percentage adjustment for the font's character spacing.

Flip Angle
Specifies the angle, in degrees from the vertical, at which point rotated text is flipped, or mirrored, in place. At this point the text starting point becomes the ending point and conversely.

Override
When you edit annotation in ArcMap, and change the properties of it, for example; size, font, color, and so forth, this applies an override on the changed annotation. ArcGIS starts drawing the annotation first using the symbol in the symbol collection, and then also applies the overrides stored in the individual annotation's record in the attribute table Override field. Each value can represent a single override or a combination of overrides.