A Deep Focus Shot Analysis Model
A deep focus shot has a long depth of field, which essentially means there is a long distance that is seen clearly, in focus. This shot from Citizen Kane is an example of a deep focus shot (although the entire film is pretty much famous for being shot in deep focus).

If you're unfamiliar with depth of field and camera focus, you might find it helpful to look at these examples and an explanation here.
A deep focus shot has a long depth of field, which essentially means there is a long distance that is seen clearly, in focus. This shot from Citizen Kane is an example of a deep focus shot (although the entire film is pretty much famous for being shot in deep focus).

What are we meant to be looking at?
Cinematographers can use focus, or a focal point, to guide an audience's eye to whatever it is they want us to focus on. You're probably so used to this that you don't even realize you understand how it works: think "portrait mode" on a camera where the background is blurred out. With the background blurred out, this enhances the crisp clarity of the person in the portrait. The blurring of the background tells us not to focus on it, not to worry about whatever is back there.
With deep focus, viewers and audiences are challenged to determine what it is they are to be looking at. Some argue that a deep focus shot is more like real life, where we can look at the world around us and it's up to us to choose what to focus on.
The Boardinghouse Shot
So -- what are we meant to focus on? Is it the conversation in the foreground? The boy beyond the window in the background?
Well, films involve motion and sound - which you aren't getting here with the shot featured on this blog, but it's important to consider those aspects as well (especially if you're conducting a formal film analysis 😉). I'll describe those things as we move through the shot a bit.

If we consider some of the "rules" of composition, our eyes naturally tend to focus on the intersecting points of the grid featured here across a frame.
Young Charlie Kane in the Window
So, in the boarding house shot from Citizen Kane, our eye is already tending towards either the boy beyond the window or the man and the woman conversing in the foreground. But, the dark clothing worn by the characters in the foreground starkly contrasts the white snow in the background, and since there's even a little box created by the window to frame the white "image" beyond, our eye can't help but go to the young Charles Kane chucking snowballs out back. He is so small, being a child, but also literally small compared with all of the adults in the scene, since he is so far away.
Thatcher and Mrs. Kane in the Foreground
As we start to consider the action of the scene, then we're meant to focus on the conversation between the man, Mr. Thatcher (a banker), and the woman, Kane's mother, in the foreground. Thatcher and Kane's mother are discussing their estate, as they've just come into more money than they'll ever know what to do with. This is an important conversation, it's in the foreground of the shot, both Thatcher and Mrs. Kane are the largest characters physically in the room. Yet, Mrs. Kane is almost 2-dimensional, a silhouette featured from the side in contrast with the full face and even the fuller spectrum of black/gray we can see of Thatcher's suit as compared to Mrs. Kane's black dress that effectively erases her body into a black blob that is the edge of the frame and Thatcher's coat arm. With regards to sound, we can hear Thatcher and Mrs. Kane discussing the details most prominently, but young Kane's voice shouting from the open window competes with their conversation, just as his dark clothing against the white snowfall in the window competes with our visual focus in the shot.
Kane's Father in the Midground
In the midground (MG), between the decision makers and the young Kane outside, is Mr. Kane. While he stands taller than everyone, he looks physically smaller than Mrs. Kane and Mr. Thatcher. He is also dressed more casually, his vest unbuttoned. His black pants help more of him to disappear in the same way that Mrs. Kane's black dress makes her body disappear. Yet the softer lighting on Mr. Kane allows us to see the varied grays of his shirt and vest, which almost camouflage him into the vertical wooden boards of the room. Although he seems to literally be in between Charles Kane and his mother and Thatcher, Kane's father is not in between them in the shot, he's framed to the left, which might signify how he's not involved in this conversation where Kane's mother is handing over legal guardianship of her son to Mr. Thatcher, who is framed between them all.
Finally, Thatcher and Kane are almost in the center of the shot together, while Kane's parents are towards the edges of the shot, as they are nearing the edge of Kane's life by transferring guardianship.
You're meant to be looking at everything in the shot
At least with Orson Welles, and I always felt the same watching Hitchcock films, you're meant to be looking at everything in the shot. There are many things here with significance, but really it's that all of the pieces (the framing, the lighting, the costumes, the sound) inform the action of the scene: everything here further reinforces the transfer of guardianship from Charles' parents to Mr. Thatcher, a pivotal moment that changes the course of Charles' life. The sound of Charles' shouting beyond the window is in tension with the conversation between Thatcher and Mrs. Kane, competing for our attention the way Kane goes on to compete for attention later on in his life.