What Does Come Mean to you?

I am trying to figure this out. My Mom and Dad keep yelling 'come'...what does it mean? Whenever they yell it, I sit there and wait for them to come to me, but they don't, so I am really getting confused. Then they yell 'house' and I wait for them to go into the house, but, again, they don't. I have been working for a long time now on training them, and for some reason, they just can't get it. I think that after a certain age, (not saying they are old or anything like that) humans just can't be trained anymore. But, as any good dog will do, I will keep on working on them and give them every opportunity to improve. I have noticed that their voices are now able to yell much louder, so apparently, they are getting better at it!