@nosleep@neckbeard.xyz it's called an "em dash" and I've noticed it's used because you *could* but есть in there but 99,9% of Russians just ... do not.
eg.
«Москва - это столица России»
или «Москва есть столица России»
are *technically* valid but the first one makes you sound like you do not know anything about how Russia works and the second you sound fucking retarded.
It's a joke among those learning Russian that «—» just marks the present tense of быть