Arduino boards are able to read inputs - light on a sensor, a finger on a button, or a Twitter message - and turn it into an output - activating a motor, turning on an LED, publishing something online.
TEMPERATURE SENSOR
Temperature Sensors measure the amount of heat energy or even coldness that is generated by an object or system.
BATTERY HOLDER
Function of a battery holder is to keep cells fixed in place safely and securely while conveying power from the batteries to the device in question.
LCD
The use of LCD is to indicate a person temperture by programming the LCD
RESISTOR
Resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.