When i connected a photoresistor (LDR) to the analog input…and wrote a code to get the input from it on the serial monitor…i could see some numbers on the Serial monitor…what do those numbers represent…voltage , current or something else ?
The analog inputs connect to an analog-to-digital converter - calling analogRead() sets the converter going on the pin you specify.
The result is a 10 bit value, ie a number between 0 (representing 0V) and 1023 (representing 5V). If you want a value in volts try something like:
float voltage = analogRead(mypin) * 5.0 / 1024 ;
To get a meaningful result for an LDR you need to wire the LDR as a resistive divider with another fixed resistor. Each end of the divider goes to 0V and 5V, the centre connection to the analog pin. Check out http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1226029330