One Pagers are executive summaries of your business plan and investor deck that are distilled into one page showing all the main items.
Ideally, the one pager will include the following information - the Need that the startup aims to solve or alleviate, the product \ solution, the market size in number of potential customers and in potential revenue, the team, the stage the startup is at and the amount of funding that it is looking to raise.
I offer FREE evaluation and written feedback for any startup.
In addition, if you feel that you are stuck with answering some of the above questions, or that the answers that you have make for more than 1 page. I would be happy to assist you in distilling the essence of what needs to be written down.