Today's reading gives us two really important and related theological points. Don't get intimidated by the word "theology;" all it means is knowledge or study about God. For Paul, especially, but for us too, theology is always personal. It's not abstract, academic thinking, but thinking about the God we trust and who loves us. The first point Paul makes here is the heart of the protestant reformation (though the difference between Catholics and Protestants on this has always been a difference of emphasis, not an actual disagreement.) Paul says we are justified by grace through faith, not by our works. What that means is that God saves us because he loves us, not because we have earned it. There's nothing we can do to earn salvation, and nothing we need to do. Jesus already did everything necessary for our salvation.
The second part is that once we know God through Jesus, we're normally filled with gratitude for what Jesus did for us. We're also often filled with love for others because we know how much God loves us. Those two things, gratitude and love, lead us to want to help others. Our faith leads us to do good works, and those good works usually strengthen our faith even more. God loves it when that happens, and God is always happy to provide us new opportunities to serve and grow in our faith.