I just anyone to tell me about the led on the top of the front of my iphone 8 plus

It’s the ambient light sensor actually. The iPhone 8 includes a True Tone Display. The goal is to make the display white balance correct so the whites actually look white and colors are accurate. That ambient light sensor can detect the light to change the brightness and temperature of your display to match the environment you’re in to keep your display properly balanced color and not to bright or too dark. If you go to settings > display & brightness and toggle True Tone off and on you’ll be able to see it at work as it’ll turn warm or cool and gradually perfect the color and display brightness to match your environment.

Do you mean the dot above the speaker ? That's the proximity sensor for when using the phone as a phone and holding it to your ear, it should turn the screen off.

I believe you mean the proximity sensor. In calls as well as in a variety of apps it allows the screen to go dark instantly when something is in close proximity to the sensor.

The larger dot to the side of the speaker is the front camera.