In short, any time you land at an airport that is not the one you took off from, you can log it as cross-country. The 50-nm rule applies when you're going for a rating.

Say you have 40 hours of flight time that was spent going to and from an airport 15 miles away. You also have 60 hours of flight time spent going to and from an airport 60 miles away...

You have 100 hours of cross country. You can put that on your resume, use it for 135 reqs, whatever... It's point to point and loggable as cross country.

HOWEVER, when meeting the requirements for a rating (commercial, ATP, etc.) you can only count the 60 hours that are >50nm. Because you are using those hours to meet the requirements for a rating.

You have 100 hours cross country, but only 60 are applicable when going for a rating.