Learn German: Ich kenne die Sehnsucht nach dem Idol sehr gut. - I know the longing for the idol very well.

In German, many nouns have fixed prepositions, just like verbs do. The noun die Sehnsucht (the longing or yearning) is almost always followed by the preposition nach to express what it is you are longing for.

Why is it dem Idol instead of das Idol?

The preposition nach always forces the following noun into the dative case. Since das Idol is a neuter noun, its dative form is dem Idol. Whenever you learn a noun with a fixed preposition, you also have to remember which case that specific preposition triggers.

Why use kenne instead of weiß for 'know' in this sentence?

This is a good refresher: you use kennen when you are personally familiar with a noun, such as a person, place, or feeling (like die Sehnsucht). You use wissen when you know a fact or a piece of information, which is usually followed by a clause rather than just a direct object.

Does das Idol mean the exact same thing as 'idol' in English?

Yes, it is very similar. In German, das Idol typically refers to a role model, a celebrated star, or someone you deeply admire. It makes perfect sense in this context to feel Sehnsucht (longing) to meet or be near them.