What is/was a "Red Aid Center"?

In George Orwell’s account of his volunteer service in the Spanish Civil War, [I[Homage to Catalonia,* he refers a couple of times to something called a “Red Aid Center.” He provides few details – presumably he expected his British-leftist audience to be familiar with the term. I got the impression that it was some kind of public relief or community center run, not by the state, but by a leftist political party. Does anybody know more? Do “Red Aid Centers” still exist, anywhere?

From this site

A sort of Communist Red Cross, then? Does it still exist? Certainly the Spanish organization would not have survived Franco’s victory – but were there branches in other countries?