temp1=temp1*0.245*2
this actually tells to the compiler to read the value of temp1 from the ram, multiply it with 0.245 and with 2 and store the result back to the variable temp1
I don't know why you think that this would be a problem to do.
char temp[10]
this declares an array of 10 characters , temp[0], temp[1], temp[2], temp[3], temp[4], temp[5], temp[6], temp[7], temp[8], temp[9]
note that when you declare char temp[x] (or any array) you can access temp[0]..... temp[x-1]
it is just a group of 10 char type variables placed in contiguous memory space, you can assign any value to each of them but we usually use this array type as a string to hold some text (as letters in each position)
you can declare any type of array, int temp[10], long int temp[10] etc
In your code you get a result from the ADC, for example 100, then multiply it 100*0.245*2=450
and then use INTToStr function to convert the integer 450 to a string '4' '5' '0' that is stored in the temp array to be shown later in the LCD
Alex