When your dentist performs the extraction you should expect that you will feel a lot of pressure, here's why:
The root portion of a tooth is firmly encased in bone (its socket) and it is tightly bound into place in this socket by a ligament.
During the extraction process the dentist needs to expand the socket (widen and enlarge it) and separate the tooth from its ligament to a point where the tooth is loose and free to come out.
The bone of the jaw is compressible to some degree. That means if a dentist can apply firm pressure to a tooth, forcing it against one of the sides of its socket, the bone in that area will become compressed.
The net result is that the socket becomes slightly enlarged. After repeated application of pressure to a tooth, from many different directions, the entire socket becomes larger. The ligament that holds the tooth in place will become detached from the tooth too.
Finally at some point, enough space would have been created and the ligament from the tooth will be separated enough for the tooth will come out. Dentists have a variety of tools they use to manipulate and apply pressure to teeth. Some of them are specialized pliers termed "extraction forceps." Dentists also use levers that are called "elevators" (they look somewhat similar to small screwdrivers).
Usually a dentist will use an elevator first. These tools are intended to wedge between the tooth and the bone surrounding it.
The force the dentist applies to the elevator in turn places pressure on the tooth. This action on the tooth helps to expand its socket and separate its ligament. It's somewhat common that a tooth can be extracted with just the use of an elevator.
Understanding the dentist's use of extraction forceps is more straightforward. The dentist will grasp the tooth with the forceps and then firmly and deliberately rock the tooth back and forth. They will also rotate the tooth as much as it will.
The combination of these tooth movements expands the tooth's socket and separates its ligament.