
How it works:
To move, you'd use the DS control pad. To use the first option of something, press A. To open the menu, press B. After pressing B on something, the menu would appear on the bottom screen. Start opens up the menu, and select opens up the world map. L and R move the screen, and X and Y will be mentioned later.
Since there isn't as much space on the DS, things had to be in more menu's. The combat swords have three tabs. One to choose your attack style, one to handle all summoning stuff, and one to change your equipped items.
The stats page has stats, quests, and achievement diaries.
The spell book has spells and prayers. Also, you can hot key up to two of either spells or prayers to X and Y.
The item pocket has only items.
The friends section has three tabs, but it's only available on online play, apart from the NPC chat. It has friends, ignore, clan chat, and NPC chat, which is when NPC's talk to you (switched to this tab automatically when needed).
What's different? Firstly, the report option is gone. Second, the camera is a bit different, since it can't move vertically. Also, the experience is a bit different. It doesn't take near as long to get to level 99 in stats. The experience of level 99 would only be 1,300,000, which is ~1/10th of what it is in the actual game. This way, you have some chance of getting all 99 stats without throwing your life away.