Resistance is how hard it is for current to get through. It is measured in ohms (Ω). A conductor has few ohms. An insulator has so many that almost no current gets through.
The meter is set to ohms. It pushes a tiny current from its own battery through the piece and works out the ohms. That current is far too small to feel. Only measure ohms on something that is turned off. Never do it on a live circuit.
Wire ohms come from NEC Chapter 9, Table 8. The table is for stranded, uncoated copper and aluminum, in ohms per 1,000 ft at 167 °F (75 °C). For 12, 10, and 8 AWG, copper has 1.98, 1.24, and 0.778. Aluminum has 3.25, 2.04, and 1.28.
Heat raises a metal wire's resistance. The heat change follows the notes to Table 8. At 68 °F (20 °C) the wire has about 18 percent fewer ohms than the table. At 194 °F (90 °C) it has about 5 percent more. The last number before the equals sign in the arithmetic is that change.
Twice the length gives twice the ohms. A smaller AWG number means a thicker wire. A thicker wire gives current more room, so it has fewer ohms. Aluminum starts at 12 AWG here. That is the smallest aluminum wire size in 310.5(A).
The meter face uses the ranges of a common electrician's meter. Its lowest range reads in steps of 0.1 Ω, so it rounds wire to one decimal. Its own leads also add a little. The Resistance readout shows the value worked out from the table.
The red tint on the wire shows heat. Real wire this warm does not glow.
That meter tops out at 40 MΩ (40 million ohms). Rubber is far past that, so the meter shows OL, which means over limit.
The skin numbers are typical figures from NIOSH (publication 98-131). With dry skin, the body's resistance may be as high as 100,000 Ω. Wet or broken skin may drop it to 1,000 Ω. These are the body's resistance at 120 volts. Real values change a lot with sweat, grip, cuts, and voltage.
A meter on skin uses only a few volts, so it reads much higher than these figures. That is why the skin picture shows the figure and not a meter.
Skin is a poor conductor, not an insulator. At 120 volts, 1,000 ohms lets through enough current to stop a heart. Never test this on yourself with a live circuit.