Refer to figure.
Parasite drag describes the drag caused by the non-lifting components of the helicopter, most notably the fuselage and its components and is made up of Skin friction, Form (pressure) drag and Interference drag. The parasite drag is only considered as a function of the forward speed of the helicopter.

As forward speed increases, the parasite drag increases too. More specifically, the parasite drag increases with the square of the speed and quickly becomes very significant, unlike rotor profile drag which increases only slightly with forward airspeed.

Induced drag is the drag which results from creating lift. In other words, the energy required to turn the air. It is absolutely linked with lift, so this type of drag is sometimes known as “Lift Dependent Drag”. Because the lift generating components of a helicopter are the rotor blades, induced drag is specifically associated with them.

As forward speed increases, the induced airflow decreases, increasing the effective angle of attack, so the lift required to maintain altitude becomes less, as a result the induced drag decreases.

Rotor Profile Drag is the drag created when the rotor is moved through the air, when no lift is being generated and it is made up of the blades form (pressure) and skin friiction drag.

Rotor profile drag would at first seem to be independent of forward speed, as the increased drag on the advancing blade would be offset by the reduced drag of the retreating blade. In fact, this effect is proportional not to the blade speed, but to the square of the blade speed. Although, it is almost constant at very low airspeeds, rotor profile drag rises gently as airspeed increases.

The Total Drag curve is the sum of all the drags, mostly affected by the induced and parasite drag and almost not at all from the profile drag, since it remains almost constant for the various speeds.

More specifically, the total drag curve is initially affected by the induced drag curve, following its inclination until reaching at its lowest value where the decreasing induced drag becomes equal to the increasing parasite drag, as speed increases. After this point, the total drag is mainly affected by the parasite drag and follows a positive inclination.