Dot-notation is used to express the relationship between an object and it’s properties (and sometimes methods). An example of dot notation would be building.streetAddress. In this example, the object would be building and the property would be the "streetAddress." If the "streetAddress" property were also an object, you could further use dot notation to identify the street name in the building’s address like this: building.streetAddress.streetName.
{ "building": { "streetAddress": { "streetNumber": "104", "streetName": "Main st.", "city": "Portland, "state": "Oregon", "country: "USA" } } }
Dot notation can also be used in programming to call a method of an object (a function that belongs to that object). In the example above, the building object might have a method that calculates the current occupancy of the building. So if you called the "occupancy" method on the building object like so: building.occupancy(), you’d get a number like 42. And if you called that number in the middle of the night you might get a return value of 0.
In summary, if someone says that you can access a variable using dot-notation, this means that the variable is nested in one or more objects and you can refer to that variable by specifying the relationships between the properties using… dot notation.