Short answer: a regular hexagon with side 2 has apothem √3 ≈ 1.732, area 6√3 ≈ 10.392, interior angle 120°, exterior angle 60° and 9 diagonals.
One triangle, repeated
Every regular polygon is n identical triangles meeting at the centre. Each has base s and height the apothem, so the area is n × ½ × s × apothem — the perimeter times the apothem, halved. That is why the apothem is the number worth computing first.
Worked example
A hexagonal nut across the flats is measured by its apothem, not its side: for an apothem of 10 mm the side is 2 × 10 × tan(30°) = 11.547 mm. The page converts in the other direction, which is how a drawing across the corners is turned into a cut length.