Hello there!
Have you seen a camera before? It's a device that helps us capture pictures of things we see around us.
Now, cameras have something called 'Zoom'. You know what that means, right? It's just like when you use your fingers and thumb to pull a tiny object closer to your eyes to see it better.
So, when we talk about 35mm equivalent focal length in cameras, it means the camera's zoom lens can capture pictures of things that look just like how they would appear to us if we were physically standing at a distance and looking at them using our eyes.
For example, if you take a picture of a bird that is really far away with a camera's zoom lens that has a 35mm equivalent focal length of 50mm, the bird will look just as big as it would look to you if you were standing at the same distance as the camera and looking at the bird.
So, a 35mm equivalent focal length is just a way of measuring how close or far a camera can "bring" an object to its lens, and how that compares to our own human vision.