Please help explain sprintf

I'll try to explain it symbol by symbol:

$ - this symbol will precede the resulting number. You can put virtually anything here. If you put ABC instead of $, the resulting string will be "ABC100.50"

% - This is a placeholder where the number will go in the whole formatting - things that precede this symbol will be literally interpreted as things you want to print in front of the number

0.2 - or even simply .2 ("$%.2f") tells the method how many decimal places you want to print, two in this case. 0.1 would give you one - "$100.5", 0.3 would give you three - "$100.500" etc.

f - this is the type you want as a result. "f" stands for floating point number. "i" would give you an integer (no decimal places at all).

number - that's the variable you are passing to the whole sprintf formatting method. You can pass a variable, like Jason did, or an actual number, like this: sprintf("$%0.2f", 100.5)

Do some experiments to see this in action.