die Ostseite
east side
The side of an object, building, mountain, or area that faces east.
Die Fenster auf der Ostseite des Hauses bekommen die Morgensonne.
The windows on the east side of the house get the morning sun.

east side
Loading your saved state.
east side
The side of an object, building, mountain, or area that faces east.
Die Fenster auf der Ostseite des Hauses bekommen die Morgensonne.
The windows on the east side of the house get the morning sun.

The word is built very logically and consists of the compass direction 'Ost' (east) and the noun 'Seite' (side). So it literally refers to the side that faces east.
Die Ostseite des Berges ist besonders steil.
The east side of the mountain is especially steep.
Following the same pattern, you can form the sides for all compass directions. The other words are 'die Westseite' (the west side), 'die Südseite' (the south side), and 'die Nordseite' (the north side).
An der Südseite des Hauses haben wir eine große Terrasse.
On the south side of the house, we have a large terrace.
To describe a position, the preposition 'auf' with the dative is usually used: 'auf der Ostseite' (on the east side). To show belonging, you use the genitive or 'von': 'die Ostseite des Gebäudes' (the east side of the building).
Auf der Ostseite der Insel gibt es einen wunderschönen Strand.
On the east side of the island, there is a beautiful beach.
east
'der Osten' and 'die Ostseite' both have to do with the direction east. 'der Osten' names the cardinal direction or an eastern part of a larger area. 'die Ostseite' is more specific: it means the side of something that faces east, for example of a house, mountain, or park. You can confuse the words when talking about location. 'Im Osten' (in the east) fits for a direction or region. 'Auf/an der Ostseite' (on/at the east side) fits when a specific object has different sides.

An der Ostseite des Hauses scheint morgens die Sonne ins Schlafzimmer.
On the east side of the house, the morning sun shines into the bedroom.
Im Osten der Region liegen viele kleine Dörfer.
There are many small villages in the east of the region.