Lux (lx) measures illuminance: the light arriving at a surface. One lux equals one lumen per square metre.
Reading fixture specifications
A lux figure needs context. Check the measurement distance, CCT, dimming level and the reflector or other optic used. A centre-beam reading describes one point; it does not show how evenly the fixture illuminates the whole area.
Compare fixtures using equivalent conditions. A narrow reflector can produce a high reading at the centre while covering less of the scene.
Lux and exposure
Lux alone does not specify a camera aperture. Exposure also depends on ISO and exposure time, plus the calibration and measurement method used. Use a light meter or a suitable exposure calculation with those settings entered.
Lux and foot-candles
Both measure illuminance. One foot-candle is approximately 10.764 lux. For example, 100 foot-candles is approximately 1,076 lux.
Related reading
CCT · Browse lighting equipment · Incident Light Meter · Stop
References
Sekonic: lux, foot-candle and cinema exposure metering · Sekonic L-398A manual: illuminance measurements