It's because "are you coming home?", despite being gerund, refers to the future. In English you could say: "tomorrow I'm having a party", but you could never use the gerund in Spanish because the action is not taking place when you are speaking. ¿Estás viniendo a casa? = Are you on your way home? ¿Vienes a casa? / ¿Vendrás a casa? = Are you coming home? Will you come home? Hope it's clear. Regards.

The gerund is used to explain that a certain action is happening at the same time when we are talking. For example, and using your sentences: -"¿Vienes a casa?" (Do you come home?) -"¿Estás viniendo a casa?" (Are you coming home?) In the first case, we could imagine calling for his husband while he is at work and a little bit late so, she want to know if she has to cook for both (for example) And in the second case, she call him to ask if he is going home (for example, if he is on the bus). The main difference is that the present simple is used with a future sense whereas the continuous form is used to describe "2 actions"

Doug, Your problem is that you are thinking in English to understand. In Spanish you could perfectly ask: "¿Estás viniendo a casa en estos momentos?" because you want to know exactly how many minutes do you have before he/she arrives. But anyway, in a regular situation you would ask : Vienes a casa hoy?, mañana? etc That means that the present continous in Spanish has a similar usage than in English but NOT EXACTLY THE SAME. If you want to get used to it, just listen, read, talk with natives etc.

Hi! If you ask 'estas viniendo', you want to know if the person is going (to your home in this case) right while you're talking to him/her. This is way you use de gerund, to refer to an action which is happening at the moment that it's being mentioned. Vienes could be any time. Tomorrow, next week, next month, next year, etc. Greetings! REF.: I'm a Certified Spanish Teacher.