A regular clean maintains a home that is already in decent shape. Kitchens and bathrooms get cleaned and sanitized, surfaces get dusted, floors get vacuumed and mopped, trash goes out, beds get made. It is designed to be repeatable in a few hours, which is exactly why it is affordable enough to do every week or two.
A deep clean is a different job wearing a similar name. It goes after what accumulates over months: grout lines, shower door tracks, the inside of the oven and refrigerator, cabinet fronts, door frames, switch plates, baseboards, window sills and tracks, ceiling fans, vents, and the floor behind furniture that has not moved since you bought it.
Here is the two-minute test. Walk into your bathroom and look at the grout and the base of the toilet. Then open a kitchen cabinet door and look at the top edge and the handle area. If those places look tired, no amount of regular cleaning will fix them, because a regular clean does not have the hours in it to scrub them. You need one reset first.
That is why most cleaning companies, including us, recommend starting with a deep clean and then moving to a recurring schedule. The deep clean brings the house up to a standard, and every visit after that holds it there in less time and for less money. Booking regular cleans for a house that has not been deep cleaned in two years just means paying every two weeks to fall slightly behind.
The other direction is worth saying too: if your home is already maintained, do not let anyone sell you a deep clean every visit. Once or twice a year, plus before holidays or after a renovation, is usually plenty. A good cleaner will tell you that instead of quietly upselling you.