What was the view on premarital relations in the times of the gemara? To be clear, this is not a question of what is or isn't permitted. This is a question about historical practices; historically how did Jewish communities view the idea of cohabitation or relations out of wedlock?
One is "marriage through intercourse", that is, the man has intercourse with the intention of making her his wife by so doing. This practice is rabinically prohibited- they are liable for lashes from the Beit Din for getting married in this fashion- but by Torah law, it is effective, and they are considered married and require a get to divorce.
The other type of pre-marital intercourse is called "Z'nut", which gets translated as "prostitution" or "promiscuous sex" or "promiscous relations". This type of pre-marital intercourse is also prohibited but does not create a marital relationship.