Obstacles test a character's resourcefulness and resolve. Sometimes they can even reveal modes of thinking, priorities, and values. Finally, obstacles add uncertainty, provoke curiosity, and can create or augment suspense and tension. Events or situations. Furthermore, obstacles can be short, intermediate, or long-term in duration.
Some obstacles pop up quickly and are disposed of, overcome, or dodged just as quickly.
These can add zest to a scene or action which would be bland or lacking energy if it unfolded without any such obstacles. Some object-obstacles could take longer to overcome several minutes, several scenes, even a whole sequence or act. For instance, a crippled plane blocks the only available runway which is needed for an emergency landing. A mountain stands in the way of an intended destination. A desert must be traversed.