Which sensor to detect light?
Number 23 in the list says photoresistor, corresponding to module KY-018 in your kit, which is what you called photocell (a photocell is another type of sensor to my knowledge).
As the name states, a photoresistor is a device changing it's resistance depending on the amount of light it detects/receive.

A photoresistor usually looks like:


In order to get a meaningful reading from an LDR you need to convert the resistance into a voltage which the Arduino's ADC can read. The simplest method is to use a voltage divider: the junction between the LDR (photoresistor) and R1 is the node to connect your analog pin to get your readings, which will be a voltage that is a proportion of the supply voltage (5V) defined by the ratio of the two resistances.

The KY-018 module mentioned above already provides all the necessary and provides you 3 pins: 5V, ANALOG and GND.







simulate this circuit &ndash; Schematic created using CircuitLab