The Wolfram Language Paclet Repository lets you browse all paclets, browse by functional category, see the current Featured paclets as selected by Wolfram staff, and search by name, publisher ID, keyword, etc. Each paclet has a description and some documentation on its front page, and will typically have additional documentation like tutorials, guide pages, and function reference pages that can be viewed as well. Those documentation pages will appear in the in-product documentation viewer after the paclet is installed.