"He is reading while he is eating."
Translation:Il lit pendant qu'il mange.
I think "alors que" is more like "whereas". It would be used when contrasting two things. For instance, "Il porte des chaussures alors qu'elle porte des bottes." (He is wearing shoes, whereas she is wearing boots.) I will admit, however, that I'm still learning, so maybe a mod could step in to verify if this is correct or not?