A sector includes a central angle and two radii.

A segment includes a chord and its corresponding arc.

A sector looks like a pizza slice or wedge.

It is crescent-shaped.

Centre of a circle is included in a sector.

Centre of a circle is not necessarily included in a segment.

$\frac{θ}{360°}×πr^2$, where θ= central angle and r= radius

Segment Area
= Sector Area - The Area of the corresponding triangle
= $\frac{θ}{360°}×πr^2-(\frac12×r^2\sin⁡θ)$