A local coordinate system: an origin plus three perpendicular axes. X is taken as given, Z is X cross Y, and Y is adjusted to be square to both.
Origin, from a wire; replaces the typed value.
X axis, from a wire; replaces the typed value.
Y axis, from a wire; replaces the typed value.
Values the block gives besides its output. The editor lists them under Properties, and an input can read one by reference.
Where the frame's three axes meet.
The affine map from this frame's local coordinates to world coordinates.
The frame's unit X direction.
The plane spanned by X and Y; its normal is the Z axis.
The plane spanned by X and Z; its normal is the Y axis.
The frame's unit Y direction.
The plane spanned by Y and Z; its normal is the X axis.
The frame's unit Z direction.