That’s so broad of a question it is really tough to answer. You might want to throw some specific questions out there so we have somewhere to go with it. An example of specific would be “How often do you need to change leadcore line and how do you know when it is time to change it?” or something like that.
There are lots of ways it can be used. Pulling various different types of cranks is probably the most common. Anything from floating stick baits to deep diving baits. Not only can you get baits deeper than normal, I think the leadcore changes the action of the bait a little bit as well.