What is expressionism?

I think expressionism has to do with loss. More specifically death. The sheet that we got today in class with the poems made it, for the most part clear to me. Many of the poems sounded like soldiers from the war speaking to their wives. For example,  in the poem Lobspruche it says "They had buried me. I heard them say i was dead. But the shiver of resurrection went through the earth and the floods of eternity reached me with their starless blue days.....you kissed me and i became like your lips: somewhat pale...." What i got from that was that she got in one last kiss before he died. Many of the poems also sound like experiences that these people went through that were rough. Since this new art form came from WW1 it has to do with a lot of rough experiences put into art. I would definitely want to look more into this.