The 500 mA per-channel current is the maximum the internal switch can sink continuously. The 40V maximum supply voltage gives headroom on a nominal 12V or 24V automotive bus.
PWM dimming and thermal range
PWM dimming is handled by toggling the enable pin or the input supply, giving a wide dimming ratio without colour shift. The 8-SOIC package dissipates heat through the leads and the PCB copper; for continuous 500 mA operation at high ambient, a thermal via pattern under the package is recommended to keep the junction within limits.
For a BOM line requiring a linear LED driver with these ratings, this part can be specified into production without a last-time-buy concern.