Why does the toilet bubble when flushed?

When a toilet bubbles when flushed, it is usually due to a blockage in the Plumbing system. The blockage causes air to get trapped in the pipes, leading to the bubbling effect when the toilet is flushed. This can be caused by various factors such as a clog in the pipes or a malfunction in the vent system. It is important to address the issue promptly to prevent further plumbing problems.