A chord made using the minor third and perfect fifth on top of a root note is known as a minor triad chord.
Another way to think of it is by imagining a minor third interval with a major third interval stacked on top of it.
Let me illustrate my point with an example:
Suppose you want to create the Gm piano chord, you start with the root note G and form the minor third which gives us the note Bb. So now we have the notes G and Bb.
Next you add a major third interval on top, starting on the note Bb. This gives us the note D.
So by adding a minor third interval with a major third interval, we end up with a minor triad chord.
Another method to form any minor chord is by picking a note on the keyboard, count three steps to the right of that note and the note you land on will be the second note in the minor scale.
Once you find the second note, count four notes to the right of that note and the note that you land on will be the third note of the minor piano triad.
This counting method can be used to form any kind of minor chord.
The following infographic will help you understand this concept further: