Definition of good run
A "good run" or "run good" is a short or long pass during which you are lucky. When we are in a good run, we have aces and our opponents have kings, we have stronger brelans than our opponents, we have ace colors when our opponents have king colors, in short, we have the momentum, the wind in our sails. The "good run" is opposed to the "bad run", a pass during which our aces are cracked and during which no matter how strong our hand is, we always have the second best hand.
The good run and the bad run, it's in our head
Obviously, cards have no memory. If you have 3x aces in 3 hands, it's a good run. But in reality, it is only your mind that notices because you will have aces in all 221 hands over the long run. The good run and the bad run exist only in our mind, so you shouldn't give them too much importance. However, it can give you a lot of momentum. If you win 4 big pots in 15 minutes, it may discourage some players from playing against you.