I am also hearing that security tokens are not traded on bigger exchanges. Can I know that what is meant by security tokens?
A security token is a crypto token that passes the Howey Test is deemed a security token. These usually derive their value from an external, tradable asset. If you want to read more about what a security token is with some examples of security tokens, you can read this article.
https://medium.com/@tatianakoffman/your-official-guide-to-the-security-token-ecosystem-61a805673db7I hope this answers your question and if you have anymore questions, feel free to ask away!