The second great awakening was a religious movement, or a set of ideas, regarding how a person should deal with religion and with themselves and the society. It was mostly ground in Baptist and Methodist teachings and spread through America like wildfire. The movement was about emotional and supernatural elements of life and religion and against the ideas of enlightenment.
Social reform before the civil war was always a problematic thing because there was slavery in the south, women didn't have suffrage, unions were non-existent, and there were many other problems. The most that social reformers could do was help decide which states would be slave states and which wouldn't, which more or less prevented a huge amount of slave states, but there wasn't much that could be done.
Nativism is the idea that immigration is bad because immigrants take jobs away from local population that was born in the country to which the immigrants came. Before the civil war, immigration was sometimes limited for numerous ethnic groups based on things like race or religion or similar things. For example, there was a general dislike for Catholics such as the Irish because they were a cheap workforce and it was believed that Catholicism would affect their political decisions.