All clauses are categorized as one of the following: An independent clause (shown in bold throughout this lesson) can stand alone as a complete sentence. For example: John eats eggs. (This independent clause is literally a sentence. We will use this as our main clause in the next three examples.)
In English grammar, there are two main types of clauses: independent clauses and dependent clauses. Dependent clauses can take different forms (adverb, adjective, or noun clauses), but they all share the same characteristic of needing another clause to complete their meaning.
Main (or independent) clauses can form sentences on their own. They aren’t dependent on other clauses. They are always finite (they must contain a verb which shows tense). Subordinate (or dependent) clauses cannot form sentences on their own. They are dependent on main clauses to form sentences.
You use these when you refer to something which you expect the person you are talking to to know about, or when you are checking that you are both thinking of the same person or thing.
This and these are demonstratives, which means they indicate a specific noun in a sentence. The two words are similar because they refer to nouns that are near in space and time.