As the name suggests, fibrous joints are held together by fibrous tissue, there is no joint cavity present.
A few fibrous joints are amphiarthrotic but most of them are synarthrotic.
We distinguish sutures, syndesmoses and gomphoses.
Sutures (=seams) we find between the flat bones of the skull.
At birth they are pretty much free floating plates, then they start fusing at their interdigitating junctions during our first year.
They eventually ossify in adulthood, this process is called synostosis
A syndesmosis is a connection of bones by ligaments, fasciae or membranes.
In a syndesmosis the bones are connected by a filamentous sheet or cord, like a ligament or an interosseous membrane.
The fibers are generally longer and a bit more resilient than in sutures.
Examples are the distal tibiofibular joint or the interosseous membrane that keeps the ulna and the radius together.
(Greek: gomphos = nail)
A gomphosis is an immovable articulation in which one bone or part is received in a cavity of another. We find gomphoses in the teeth where the bind in their bony alveolar sockets.
This fibrous connection is held in place by the periodontal ligaments.