What is rgba attribute in text-shadow in css?please help

Answer 1

It determines the color and intensity/opacity of the text-shadow.

https://stackoverflow.com/questions/11549757/text-shadow-opacity

Answer 2

Rather then tell you in words, you could just change the following code value to observe, you would understand more.
https://code.sololearn.com/WYq9xb0XmNGD/?ref=app