Secularism is an idea that is for dividing the Church and the government. It has nothing to do with Atheism and Agnosticism, and it's not against religion but against religious involvement in politics (so conservative politicians can't abuse it for their own political success). Despite this secular nations are likely to have a low proportion of religious people in their populations.
Usually, in secular countries abortion and same sex marriage are legal and tolerated. Scandinavian countries like Denmark, Finland, Iceland, Norway and Sweden are the most secular, and Denmark is one of the happiest countries in the World.