If you are using Single Symbology the terminology is explained below:
Shape: The shape (e.g. triangle, square, etc.) of the activity if you are using a point layer.
Fill: The colour of the polygon area or point (ensure hex number starts with a #).
Stroke: The colour of the line or boundary (ensure hex number starts with a #).
Opacity: How non-transparent you want the shape to be (0.01 is highly transparent, 1 is solid).
Size: The size of the point.
Rotation: The rotation/angle of the point.
Width: The thickness of the line.
Stroke Linejoin: Options regarding the smoothness of the corners.
Stroke Linecap: Options regarding the smoothness of the edge of lines.
Stroke Dasharray: The pattern for dash or dot patterns for lines.
Stroke Dashoffset: The offset for the pattern to the right along the line.
Add labels by choosing the Point/Polygon/Line Label Text field under the Label Style.
Leave label settings as default or change as required.
Note: Pressing L on the keyboard will turn all labels on and off in the Add & Edit data and View Data pages.