Forth I assume uses reverse polish notation: arguments before the operator.

3 4 +

for example, would return 7.

Forth uses RPN so the "verb" is last.

That is, you provide the data first (I and Forth) and the command (heart) last.

A different way to say the same: in forth, words get pushed on the stack, and popped from the stack by words that take arguments:

    code           stack
    I Forth love

    Forth love     I

    love           I
                   Forth

    ; love presumably pops
    ; subject, object args
    ; from stack - and does something 
    ; perhaps prints as side effect

I found https://www.explainxkcd.com/wiki/index.php/Main_Page quite useful for that.