From IFWiki

East is a direction. It is one of the four cardinal directions, and one of the eight compass directions. Its opposite direction is west.

East is associated with the right edge of a map; most maps are meant to be read with the north-end up. If you are facing north, then east is to your right.

The EAST command

Typing EAST means GO EAST or WALK EAST. That is, direct the player character eastward from their current location. Assuming there's an exit in that direction and nothing is blocking or hindering the character, the PC will travel east to an adjacent location.

EAST is such a common command that it has an abbreviation: E.

East in other languages

Dutch oost o
English east e
Esperanto orienten or1
French est e
German Osten o
Italian est e
Spanish este e
Swedish öster ö

1 Esperanto's words for west and east are okcidento and oriento, which means it's problematic to use o as an abbreviation for either of them. There aren't enough Esperanto IF games to see any clear concensus on how to abbreviate orienten, but or seems the most likely possibility.

Code Compare

Directions like EAST tend to be implemented both as room properties and as objects in their own right. The EAST command, however, tends to be parsed or reinterpreted as a GO command acting on the east object.

Code Compare: East
ADRIFT 4:Move East to Field begin.pngStudyField end.png
Inform 6:The e_to property and e_obj object
Inform 7:The east direction
TADS 3:The east link property, the eastDirection object,
and the defaultEastWall object