Property
From Legacy Roblox Wiki
A property is a 'member' of something. Properties are 'owned' by an object, and you reference them as you would a table. Children of an object, however, are NOT properties. (Children are objects nested within another object, like parts inside of a model.
Properties can be changed or read using the Properties tab in the studio, or by using Lua.
Properties can be numbers, strings, or any other type of value.