How does one tenderize cuts of meat?

Specifically . . . . does anyone here understand how it works? I don't cook a lot of steak, as I'm usually not happy with it when I'm done. I have good success with Tri-Tip though. I rarely buy expensive cuts either . . so that reality is on the table so you know up front. But I hear the typical stuff . . . Marinate it first, . . do a Rub . . etc etc . . But what is the actual act of tenderizing a cut of meat or assisting in it's flavor and texture enhancement? . For you culinary folks in the know . . could you impart a few pearls of wisdom here? . . I'm looking for a better understanding . . and if you have personal recipes you'd like to share, that would be fine too.