Properties of an object are the attributes of it that can be experienced (e.g. its color, size, weight, smell, taste, and location). Objects manifest themselves as clusters of their properties. Those clusters seem to change in a regular and unified way, suggesting that something underlies the properties.
The change problem asks what that underlying thing is. According to substance theory, the answer is a substance, that which stands under the change.
Photography © Rick & Brenda Beerhorst