You can also use += with text strings to directly add the variable or text on the right onto the end of the text string variable on the left.
Here are some examples.
1 "5" - 3 = 2;
2 "5" + 3 = "53"
3 2 + "7" = "27"
4 5 + 9 + "1" = "141"
Since subtraction only works with numbers 1 converts the text string into a number before doing the subtraction.
In 2 and 3 the number is converted to a text string before being concatenated (joined) to the other text string.
In 4 the leftmost addition is done first. Since these are both numbers they are actually added together and not treated as text. The result of this first addition leaves us with a similar situation to the third example and so the result of that addition is converted to text and concatenated.
This article written by Stephen Chapman, Felgall Pty Ltd.