It acts similiarly to Excel's LEFT function. It takes the text and gives you the amount of characters you want to get from the string.
Usage
LEFT(text, num_chars)
Arguments
text
the text you want to select characters from left.
num_chars
How many characters should it select?
Value
In this case we have a sentence and we want to extract first 4 characters from the sentence. Therefore we specify the argument 4 and it gives us the first word.Function will always return character class.