Text editor find and replace

Finding and replacing text is so easy and fundamental I almost feel embarrassed asking this question. However, when I recently went to perform this basic function, I was astonished to discover that Mac's approach is quite different to Windows' .

Why on Earth isn't there a field in which you type the word you're seeking to replace, below which is the field in which you type the replacement word? The text editor's equivalent only has a single field. Is this the original or replacement word?? Rather unintuitive. One doesn't seem to have the ability to nominate the replacement word, simply and without fuss as in the Windows equivalent.

I find this really disappointing. I'm sure the answer is dead simple, but it's not obvious. So I'd value someone's patience and support in answering this one for me