The USCIS website has everything from how-to guides and online tools to office locators and research tools.
Many of the sections provide detailed information on the topic. For instance, the green card section informs you about the green card for employment, family, and relatives; the application process, including form filing; conditional permanent residence and rights and responsibilities of permanent residents; etc.
If you prefer to learn about immigration in another language, you can try finding the topic in the Multilingual Resource Center. You can search for available languages and topics from a dropdown menu.
The online tools section includes a tool for calculating fees. Application forms can have fixed or variable fees. There’s also a separate section for information on filing fees.