What is this and why was it in the bottom of my oil pan? :)

The object in the bottom of your oil pan is a "baffle". Its purpose is to reduce the splashing of oil in the oil pan, which can cause air to become mixed in with the oil. This can lead to problems with the engine, such as reduced oil pressure and increased wear on the engine components. The baffle helps to keep the oil in the pan and prevents it from splashing up into the engine.

The baffle is typically made of metal or plastic and is installed in the bottom of the oil pan. It has a series of holes or slots that allow the oil to drain back into the pan, but it prevents the oil from splashing up into the engine.