what is lebensraum? Which political ideology does this idea belong
(i.e. communism, socialism, democracy etc.)

"Jeremy Noakes traces the origins of Lebensraum, identifying why
Hitler looked to the east to expand":
http://www.bbc.co.uk/history/war/wwtwo/hitler_lebensraum_01.shtml (6 pages)

Entire article:
http://www.bbc.co.uk/history/war/wwtwo/hitler_lebensraum_print.html

'Lebensraum' means literally 'room in which to live'

As in 'Gimmee some space'

Although it was an objective of Hitler's regime, I rather doubt that
it started with him, and also doubt that it ended with him.

Back in distant times, Germans had been invited to settle in the East
(I think Catherine the Great was one of the invitors).

The Austro-Hungarian Empire that evaporated in 1918 covered vast areas
of what we now call 'Eastern Europe'. Not unnaturally German was a
'common' language.

Bearing in mind that 'Germany' as we know it today was only formed in
1870, prior to that it was a bunch of Germanic States, there was not
much of a threat from migration.

The First World War landed up with Germany being cut off from the
Eastern States, and the establishment of all sorts of 'new' Republics.

It also left chunks of 'Volksdeutscher' ( people of German descent )
left in the Eastern States. The idea of a 'Customs Union' was not
totally unreasonable.
Hitler could probably have achieved it with a bunch of flowers.

Stepping forward, and ignoring WWII, also the retreat of Russia to its
core territory (plus the goldmine in Siberia)
- also ignoring the re-unification of Germany
- we see the French and the Germans (arm in arm) inviting new entrants
to the EC ... from the Eastern States.

We also see a fuss in the Ukraine - the publicity was stupendous

My take is that Russia will come to an 'arrangement' with 'Europe'

ie: 'Lebensraum' is alive and well