You are right , they both mean the same thing, the difference lies on the tense you're using.
When you say τρώω, you are talking about the present.
=Τι τρως; Τρώω παγωτό. = =What are you eating? I am eating ice-cream.
"Τρώω" changes and takes the form of "φάω" when its in the Future Simple. It becomes " Θα φάω" and it represents something that you will do at some point in the future.
Hope this was helpful ! :)