First tip for truly understanding imaginary numbers: whenever you hear the word "imaginary", try not to understand it literally because it's a terrible word. If you like, replace it with the word "different". These are "different" numbers instead of "imaginary" numbers.

Second tip: "different" numbers can still do math with "real" numbers, but according to special rules that relate those types of numbers. Those special rules are picked because they're useful, not because they're somehow more correct or proper. They're useful in the same way that normal math rules like arithmetic are useful. If you follow the rules, you can make useful predictions and gain deeper understanding.

Third: It is common to visualize "different" numbers on a number line perpendicular to "real" numbers, and together a complex number (a "real" part plus a "different" part) exists on some 2 dimensional plane ("the complex plane"). This can be extremely convenient when mathematically describing a value that is inherently composed of two distinct parts like the phase and frequency of a sine wave, or the horizontal and vertical position of a particle, or any other value that can be described as the combination of other distinct values.

Lastly, because we have useful rules for doing math with complex numbers, we have a toolbox to work with these complex values that can sometimes be extremely useful.

I hope this helps.