You can move many apps to the SD card(some will not allow it however.). on Windows Phome 8.1 you moved apps in storage sense.
The 1 gigabyte you are referring to may be the system memory. This you can not increase. It is best to run less programs at the same time if you are low on memory.
These are Windows Phone 8.1 so 10 is a bit different.
Lets move Steam
Steam can not be moved. Core programs from the OS will not even have the option.
What it looks like while moving an app.
You can set the default location to the SD card.