An enquiry form, contact form or quote form collects a customer's name, contact details and a description of the job, and sends it to your email or phone.
Shorter is usually better. Every extra field is a reason to give up. Ask only what you need to reply sensibly; you can get the rest on the phone. Letting people attach a photo of the problem can be very useful for repair, building and cleaning work.
Behind the scenes it needs spam protection, a confirmation message so the customer knows it worked, and a reliable way of reaching you. Forms that silently fail are more common than you would think.
Plenty of customers would rather not ring, particularly in the evening or when they are at work. A good form catches those enquiries while you are on a job. A broken one loses them without you ever knowing, so it is worth sending yourself a test every so often.