From MaG's walkthrough:
To move, use the directional arrows or the WASD keys. Press-hold the shift key to walk. Press-hold ctrl key to sneak. Inventory is accessed by the tab key. Press the m key for the mobile that has the e-mail, the dialogues and notes to self. For the focus band, the q key is for the next focus and e key is the previous focus. The pause key pauses the game. l key is for light attack, k key is for heavy attack and the space bar is for blocking.
As I recall, the keys can also be reassigned to suit the player. My own play was using the up arrow to move forward, and the mouse to pan around.
The focus field is used for people/objects at a distance. It isn't used all that frequently in the game.
Edit: Cross-posted with Marian's edit!