Definition of polarize
When we talk about polarizing our range, we mean a range divided into two parts, a very strong part and a weaker part. In practical terms, this can take many forms. For example, you want to have a polarized 3bet from the small blind? So you build up a polarized range consisting of very strong hands like AA, KK, QQ and AKs, but also less strong hands that play well, like 56s, 67s, 78s, etc. We can also talk about a polarized check-raise range. For example, if you decide to check-raise polarized on the flop, on a flop like A-7-8 with 2 spades, you could check-raise with a very strong hand like 77 or with a straight or flush draw.
What are the advantages of a polarized range?
The question can be asked. Good players have games that they play in a polarized way. Let's take an extreme example to make it clear. You bluff 100% of the time on the river. Eventually, your opponents will notice and before long, your bluffs will be unsuccessful. Now imagine that every time you are all in on the river, you have the nuts. Before long, no one will call your bets on the river. Now, if you have a polarized range on the river and you are 50% of the time in value and 50% of the time bluffing, it becomes much harder for your opponents to read you!