Long-Dated Asset
  
You buy a 90-day treasury bill. That’s short-dated. You don’t get much of a return, but your money doesn’t get tied up for very long.
It's like bouncing from Tinder date to Tinder date. You don’t get much out of it (emotionally speaking), but it doesn’t come with much responsibility.
On the other end of the spectrum, you have 30-year bonds, or a mortgage that you provide someone else. Long-dated assets. The return is higher, but your money gets tied up for decades.
Those situations are like getting married...a deep, meaningful relationship, but you're in it for the long haul.