The polar pattern is the preferred pick-up direction of the microphone. According to the form on the corresponding measurement plot, there are omnidirectional, cardioid, supercardioid or hypercardioid patterns, as well as figure-eight patterns.
Even if many users consider "directional microphones" to exclusively be the long, cylinder-shaped microphones known from television, in reality most of the models used in video, studio and live applications are directional microphones – regardless of their external appearance!
The name comes from the fact that these microphones only transmit the sound from (mostly) one direction at full level, while they only have attenuated (quieter) pickup of signals from all other directions. The designation "cardioid polar pattern" results from the two-dimensional display of the corresponding three-dimensional measurement: it indicates a kidney-shaped area around the front of the microphone in which all signals with approximately the same level can be picked up (in the English-speaking world this shape gave rise to association with a heart, which is why the pattern is called "cardioid"). It allows a relatively large movement range in front of the microphone, while signals from the rear of the microphone (180°) are particularly well attenuated. In supercardioid and hypercardioid polar patterns, the front recording range is increasingly reduced and the area of greatest attenuation moves back diagonally (126°– 110° from the microphone axis).
In good designs, the reduced movement range in front of the microphone (compared to the cardioid) pays off with low crosstalk from other signals (monitor loudspeakers, instruments, etc.) and higher gain-before-feedback.
With increasing directivity, i.e. starting with the cardioid and progressing to the supercardioid and hypercardiod through to the lobe type, directional microphones must be aimed more precisely at the acoustic source; signals from the side are increasingly discoloured in terms of sound quality and are transmitted at a reduced level. Microphones with a lobe polar pattern are therefore not suitable for applications in front of large sound sources such as choirs or orchestras, for instance.
This also explains why the question regarding the "range" of a microphone – for video applications for example – cannot be answered: Signals that strike the microphone from the side are transmitted more quietly than those from the front; a voice on the opposite side of a busy street will not be picked up intelligibly even by a good microphone with lobe polar pattern. In this case, physics dictates that the user must either close the street to traffic or must cross the street...