An online booking system is used when you want customers to be able to schedule an appointment with yourself. There are many online booking system platforms available, but when choosing one, it's important that it can be integrated into your website (sometimes called "embedding"). For many years, I have worked closely with clients who need a booking system on their website, and I always recommend using Acuity Scheduling. It usually takes me around 4 hours to set up Acuity on your behalf, with only a few steps for you to complete yourself (such as linking with an online payment system such as Stripe to be able to take client payment at the time of booking). Of course, you're welcome to use any system you want, but when choosing, make sure that it can be integrated/embedded into your website, and importantly, WordPress. If you choose another system, I will initially allow for up to 2 hours' worth of work to get this integrated with your new website.