There are 3 major types of cells found in your bone that must work together in a process known as resorption & remodeling to keep your bones strong and healthy.
How can this process be simplified?
If you look at your arms you might think your bone is a solid everlasting structure, but its actually being broken down and rebuilt at a consistent rate. This balance of breakdown(resorption) and repair(remodeling) is a careful balance between the cells of the bone. Any over/under compensation can lead to diseases such as osteoporosis.
The 3 major types of cells that are shown in the image below:

Osteblasts
Osteoblast cells are the bone forming cells. Osteoblast cells secrete the protein osteoid which mineralizes to become bone.
Osteoclasts
Osteoclast cell are the bone “eating” cells. This is more commonly known as bone resorption as in “re-absorb”. Osteoclast cells are located on the outer surface of bones and remove bone in balance with osteoblast cell that secrete new bone.
Osteocytes
Osteocytes are mature osteoblasts. Osteocytes are considered mature when the osteoblast cell it derived from secretes so much osteoid that it completely encases itself in bone. Essentially an osteocyte is an osteoblast that buried itself alive. The osteocyte is less active than its osteoblast form.