Okay kiddo, let's understand what a secondary dominant is!
Imagine you're listening to a song that's in a specific key, let's say the key of C major. Each note in this key has a special role, like the king or queen of that kingdom.
Now, let's say you hear a chord that doesn't belong in the key of C major, but it sounds really cool and unexpected. This chord is called a secondary dominant.
But why is it called "secondary"? That's because it's like a helper to another chord in the key. Like a sidekick!
For example, let's say our main chord in C major is the chord of G. Now, a secondary dominant can help lead us to that G chord by playing a chord that belongs to G's own kingdom (key), such as a D major chord. This D major chord is like a sidekick to the G chord because it helps make it sound even better!
Secondary dominants can come in many forms, like major or minor chords, and they can help lead us to any chord we want to emphasize. They add a lot of spice to music and make it exciting to listen to!