Question

What is meant by circumradius and inradius?

Answer 1

in geometry, the circumcircle of a polygon is a circle which passes through all the vertices of a polygon. The center of this circle is called the circumcircle and its radius is called is called circumradius.
The inradius of a polygon is the radius of its incircle.

Answer 2

The circumradius of a cyclic polygon is a radius of the circle inside which the polygon can be inscribed. Similarly, the circumradius of a polyhedron is the radius of a circumsphere touching each of the polyhedron's vertices, if such a sphere exists. Every triangle and every tetrahedron has a circumradius, but not all polygons or polyhedra do. However, regular polygons and regular polyhedra posses a circumradius.