Both these measurements are intended for determining the resistance. They differ in terms of the kind of component being measured, what translates to the range of values being measured.
In case of resistance of electronic components, it falls within the range starting from tiny fractions of an ohm and ending with megohms at the most [MΩ].
Value of insulation resistance is often expressed in gigohms [GΩ].
In order to measure such a big electrical resistance, measurement voltage has to be far higher than it is in case of standard resistance measurements. This voltage is often within the range from 100 VDC to 1000 VDC and it cannot be used for measuring resistance of electronic components because they could be damaged.
It is obvious that additional requirements connected with construction of a meter and user safety are applied in case of generating such high voltage by such small device.