You can get an idea of what Tai Chi is like by having a quick look at the Beijing 24 Form. You’ll see that the movements are gentle and harmonious.
A personal view: There is continual movement (stepping), which is extremely beneficial for good balance and co-ordination. The movements in Tai Chi have been refined over the centuries to stimulate and heal the organs and the flow of energy in the body; in fact at a high level Tai Chi is considered an internal energy art. Tai Chi has much in common with Qi Gong, and many of the movements that we practice in every class as preparation for Tai Chi are in common, but whereas Qi Gong is more immediately meditative, with repeated simple (if not easy) movements usually standing on one spot, Tai Chi is more active and initially demands more concentration on learning the moves, making it an excellent preventative for Alzheimers. As you become more proficient and stop thinking about the next move you enter into a more meditative experience which for many is the goal.
Ultimately the only way to find out if a class is for you is to try it, which fortunately is an easy and enjoyable thing to do! And you can meet and talk to the other students over a cuppa afterwards.