Historically, limestone has been an essential building material for centuries. It is strong yet workable and fairly easy to find and extract, but it is also vulnerable to the elements which leads it to degrade over time. This process is inevitable and will nearly always require professional limestone restoration, but there seems to be a common misconception around what is actually happening and the difference between erosion and weathering.
The process of erosion entails tiny fragments of rock being moved by a force such as the flow of a river, the crashing of waves or to a lesser extent the wind. These tiny fragments will impact and rub against other rocks or a large piece of rock and the friction caused will result in minute damage to both surfaces.
This damage will gradually build up over many years and eventually both moving rocks and the static ones will begin to change shape according to the erosion they have been suffering. This is why pebbles on a beach are smooth, they are constantly battered and rolled around, resulting in all of their sharp and pointy edges eventually being ground down to leave a smooth surface.