As with any professional correspondence, you don't want to seem too stiff or formal, like you're writing a letter from a Victorian template or a bad spam email asking someone to send money to a deposed prince overseas—but you also don't want to be too conversational. You're not in a dialogue yet, so it's important to treat this like a professional first interaction, and not like you're skipping several steps and asking to meet for coffee. The tone you're reaching for is, "You don't know me yet, but I'm interested in your company and want to tell you more about why."
This agreement is most often used in transactions involving a purchase. Sometimes two parties will know that they want to do a business deal together, but they aren't ready to sign an actual agreement. For example, they may agree that one party will sell his or her business for a certain price, but they do not yet agree on who will take on certain liabilities of the business. The parties can sign this document to show each other a good faith intention to work out a deal. It can also help parties get on the same page as to what they expect from the purchase.