これ (and all the other ~れ words) is a demonstrative pronoun. It replaces the subject matter, thus functions as a subject/topic, and は is the topic marker. On a side note, これ can be used with other particles, too.
この (and the other ~の words) is a demonstrative adjective.
Both words translate to "this", but even in English there's a difference
- This is a cat. (pronoun)
- this cat (adjective)
The ~こ words can be used as nouns, adverbs or adjectives and refer to location.
ここは私の家です。- Here (=This place) is my house. (noun)
そこで会いましょう。- Let's meet there. (adverb)
あそこの男 - that dude over there (adjective)
Oh I get it now
Thank you for the clarification 