Synthetic fibers are added in a recommended dosage into the concrete. These fibers may end up sticking out of the concrete and make it difficult to get the finish on the concrete to look the way you want. However, most fiber mesh will burn off if exposed to U.V. light. After a year, you should not be able to notice them.
Wire mesh is a welded metal fabric arranged in a pattern before the concrete is poured into it. It can be difficult to put together and use properly, which is why many companies have stopped using them. It typically provides support to a concrete slab.
Wire mesh and fiber mesh are used for two different reasons. Wire mesh helps prevent against cracking if the soil that the concrete slab is on settles, or if the heat causes the concrete to dry too quickly. Fiber mesh is used to prevent plastic cracking, which occurs as the concrete dries from a liquid to a solid. Neither meshes are truly necessary if the slab is being poured on sturdy soil during a cool period of time.