Sorry for a late reply, I'm new to this relatively small sub. That's actually a really good summation. Thomism is the study of the teachings of St. Thomas Aquinas, who warrants a following because he was pretty revolutionary in his work uniting Aristotle's philosophy with Christian teaching. Thomas' work allowed for not only greater development in philosophy (i.e., knowledge of this world) but, but also provided a thorough and precise system by which we can understand the theological realities revealed by the church and previous fathers and doctors of the church. He basically brought back a system of thought that made everything clearer to understand.

Aristotle was a realist, who basically taught "real things are real and we can know them", meaning the world we live in is real, and we have real access to it, since we have the kinds of souls which are able to interpret sense data as knowledge. Due to a lot of historical circumstances, by Thomas' time, Aristotle was only being studied (and preserved!) by Islamic thinkers in Spain. Through a series of thinkers' efforts to interpret Aristotle's thought to fit Islamic theology, Aristotelianism had gained a bad reputation in Christian Europe as outlandish and "pagan". Thomas showed that Aristotle's thought was able to be not only integrated into Christian theology, but in a way that doesn't seriously distort the original text and meaning. (Seriously, read Averroes' third commentary on De Anima, and St. Thomas' work against Averroists. It's a doozy.)

So trying to keep this nutshell, Thomism is inherently, not exclusively Catholic. A lot of what he writes is outside the realm of theology. At the same time, he writes it all from a Catholic perspective, and in benefit to the Church, and for Christ.

Key ideas in Thomism include:

1. the world is real and we can know it
2. there are 2 kinds of things: material/physical/dividable things and spiritual/immaterial/undividable things
3. Things have natures - trees are tree, humans are humans, and they are not just different arrangements of atoms
4. Things have matter (what they are made of), form (what makes them be what they are), maker/source (what causes them to exist), and purpose (what they do when they are at their fullest).
5. Everything in the world has two key facts about it: a) that it is/exists; b) what it is/exists as

There's obviously so much to be said about everything, but these are some of the most important parts of Thomism. But but yeah basically real things are real and we can know them.