Ramin, these are similar things! "Walk In" means you you don't have an appointment. My local barber has a sign that says "Walk-Ins Welcome!" meaning you don't need to make an appointment; you can just walk in and get a haircut. "In Person" means not over the phone, not by email, not by Zoom. When I request a book from the Library I may ask "Can you mail it to me?" and they may say "No, special orders must be picked up in person." Hope this helps!

Hello! I think that these two things are very different because they would be used in different contexts. A "walk-in" is a category of customer or client (a person who has "walked in from the street"). Customers or clients either have an appointment booked or they arrive at a place without a booking and hope to be served or helped anyway. Another meaning of "walk-in" is a space large enough for a person to alk into - usually storage like a "walk-in-closet" or for food storage which would be a "walk-in fridge or freezer". "In-person" is the way that something, or a service, is delivered - face to face or physically by the person. It can also be a way of delivering something; in-person which means that only that particular person delivers it, as opposed to having someone else deliver it. I hope that helps!