Here is information from the forum manufacturer's web site:
Quick Reply - this brings up a small text area (without reloading the webpage) where you can quickly type a short reply. Press 'Submit' when you are done typing your response. If you have a change of heart you can press cancel and nothing gets posted regardless if you typed anything or not.
Reply - This is the standard method in which you should reply when you want to reply primarily to the most recent post. The reason for this is because the subject line of your reply will autofill with the subject of the post from which you are replying. In case you were wondering, yes, you can change the subject. OK, now you are looking at what is called a text editor. Think of it as a slimmed down version of a word processor (such as Microsoft Word) in which you can format your text, add links, images, smilies, etc. More on how to format your post later. For now, type your response and press the 'Preview' button at the bottom of the page if you wish to view your post prior to submitting it. When you are done editing and are satisfied your post is ready to contribute to the forum then press the 'Submit' button.
Quote - If you wish to quote someone's post whether in whole or in part you simple press the 'Quote' button located beside the 'Reply' button underneath each post. The is very useful if you wish to make light of or expand upon a prior post. Once you press the Quote button you are brought into the same editing environment that you use to edit or create any other post. At this point, you type your response directly to that quote. When you are done replying, press the 'Submit' button.
Reply Topic - This button functions the same as the 'Reply' button with the exception that your subject line will autofill with the subject of the original post (OP). This may come in handy if you replying to a long post whose subjects may have changed over time but you want to reply to the OP. When you are done replying, press the 'Submit' button.