Is praise always good? Yes it is, because it is better than criticising someone or complaining about someone.
But is there a good way and a bad way to praise someone? Yes there is apparently.
An example is while praising kids. Singling out one kid and praising that kid alone for a correct answer is a bad way. Why? Because the kid feels rewarded for his knowledge of that one answer. This is good, but no one knows everything. At the same time, the other kids who may not have have known that one answer will feel left out.
A better way of praising is to acknowledge and call out the behaviour and the effort. Such as commending them for participating in the class. Or praising the effort required to read up before the class. By focusing on the behaviours and efforts, the praise is far more sustainable too. Because it reinforces the need to continue such good behaviour, not just in that one person, but in everyone around them. And while one answer everyone may not know, a behaviour everyone can cultivate and effort – everyone can put in!