The topic of this article is about adverbs "Потому" [patamu] (that's why/therefore) and "Поэтому" [paehtamu] (that's why) and the ways to use them correctly and not mix up with other parts of speech.
Well, the adverb "Потому" means "for this reason", the adverb "Поэтому" means "that is the reason why" (that's why). As there is no difference in "this or that reason" in a simple sentence, most often you can use any of the adverbs. The sense of a sentence would be similar.
For example: Моя машина в ремонте, поэтому я езжу на метро. - My car is in the shop, that's why I take the subway. (Моя машина в ремонте. Вот почему я езжу на метро - My car is in the shop. That is the reason I take the subway). Моя машина в ремонте, потому я езжу на метро - My car is in the shop, therefore I take the subway. (Моя машина в ремонте. Из-за этого я езжу на метро - My car is in the shop. For this reason I take the subway).
Он заболел, поэтому не пошел на работу - He had got sick, that's why he didn't come to work. (Он заболел. Вот почему он не на работе - He has got sick. That is the reason why he isn't at work.). Он заболел, потому не пошел на работу - He had got sick, therefore he didn't come to work. (Он заболел. Из-за этого не пошел на работу - He had got sick. For this reason he didn't come to work.).
Attention! Don't mix up different parts of speech. We write the adverbs "Потому" [patamu] and "Поэтому" [paehtamu] in one word. There are also similar constructions: adjectives with prepositions "По тому" [pa tamu] and "По этому" [pa ehtamu]. In this case these are two different parts of speech which we write separately.
For example: По тому лесу мы не гуляем - We don't walk through that wood. Мы любим гулять по этому лесу - We like walking through this wood.
You can also see the word "потому" as a part of the conjunction "потому что" [patamu shta] (because). We use it in compound sentences to unite its clauses, explaining the reason.
For example: Мне нравится лето, потому что тепло и каникулы - I like summer because of warm weather and vacation. Я пропустил занятия, потому что заболел - I skipped lessons because I was ill.