You can start with our glossary. (You can click on my post.) Focus on the parts of speech. (Don't worry about subjunctives.)
The two main parts of speech are nouns and verbs.
A noun is a thing. That is, it is something that either acts or is acted upon. There are concrete nouns (objects, people, places, etc.) and abstract nouns (ideas, actions, events).
A verb is a word that describes action or a state of being. For more, see the glossary. Or ask questions about specifics.