Difference between Phone memory and internal storage of Sony Xperia U

I have recently purchased Sony Xperia U and I liked the phone but have some confusion with the memory. When I saw the details of the memory i found that there are three types of memory available in this device. These are internal storage, phone memory and SD card. I am confused between internal storage and phone memory. For me, these two sounds the same but if these are coming separately then there must be some difference between these two. Can somebody over here post with the difference between internal storage and phone memory?

Internal storage of the phone can also be considered as the RAM where programs get loaded for execution. When you run any of the application or any of the file then that file gets loaded into the internal storage of your computer. So it really matters that how much internal storage you are having in your phone. If you have more internal storage then your phone will run smoothly even if you open many applications together and on the other hand if you are having less internal memory the phone cannot load many applications all together and that leads to slowness of phone. You might have noticed that when your phone gets hanged while opening many applications together, you need to restart your phone and then phone starts working normally. This is because restarting the phone clears all the data from the internal memory and makes the phone functioning again.

Other than this, Phone memory is the place where you can install your applications. All your messages also get stored in this memory only by default. It will be better for you keep this memory as free as possible because this also affects the processing of the phone. Go to the message settings and from there set the message storage to the memory card. You cannot expand the phone memory or internal memory of the phone. So it is very important to check for these memories before purchasing the phone.

I don’t think, I need to explain the external memory but to make my post complete I will do that. This is the expandable memory of the phone. There is also a limit for this memory like 8GB, 16 GB, 32GB… you can either use the maximum limit memory card or less than that. It is recommended to use less than the maximum memory allowed.