Translation:The pencil is a thing.
Thank you very much for your clarity. All of us who have looked at Japanese will probably be thinking of the distinction between wa and ga. If anyone here knows whether the Korean suffixes are used very differently from the Japanese particles, I'm sure we would all be very interested in knowing that and very grateful.
On youtube, a search will find many that are taught by Korean speakers. Often I use TalktomeinKorean, koreanclass101, and more. There's Go Billy, Go! taught very well by an American living in Korea. He interviews those other Korean speaking youtubers plus posts dialogues focused on culture. Sidebar: i just discovered SNL (Saturday Night Live) Korea, and talk, music, plus news and variety shows on youtube by MBC America, JTB, SBS. These sometimes are captioned in English, Spanish, Thai, and Tegulu. Of course, sometimes the shows use slang but it's a good way to hear how real people pronounce words.
I know nothing about Korean, but the topic and subject markers seem to be functioning something like the Japanese topic and subject markers, so I may be able to clear this up. First, I think you may have a Korean problem here, as the Wikipedia article on Korean postpositions tells me that 이 and 가 are both the subject marker, just that the former is for words that end in a consonant and the latter for words that end in a vowel. The topic marker is 은 after a vowel and 는 after a consonant. So, the difference between topic marker and subject marker is not the difference between definite and indefinite (a pencil and the pencil), nor does it have to do with all pencils. It has to do with its role in the sentence. If it is marked with the subject marker, then it is always what we would think of as the subject of the sentence. If it is marked with the topic marker, it may often be what we would think of as the subject, but it could be what we would think of as the object or even something else, like the time it happened. I often think about the Japanese topic as something separated from the rest of the sentence in English by a comma. For instance, in "My sister is a teacher," my sister is the subject. I could also say "My sister, she is a teacher," where my sister is the topic, but maybe the subject, grammatically, is she. I could also say "My sister, I love her," in which my sister would still be the topic, but she is the object, not the subject, of the verb. Now, most often, I think the topic is also going to be the subject, and the choice of using the subject or topic marker is a very subtle stylistic choice (my sister, who is fluent in Japanese, cannot tell me often why she chooses one over the other), but once again, if it has the subject marker, it is saying this is the subject (like the nominative case in many Indoeuropean languages), while if it has the topic marker, it is simply saying this is what the sentence is typically about. Now, once again, I don't know anything more than you do specifically about Korean, and the Wikipedia article I mentioned only uses examples where the topic is also the subject, but if it functions like Japanese, which in this case I think it might, then that is the distinction.
Tip: In spoken conversations topic markers are not used a lot and only function to stress the significance of something. Also, Koreans don't really consider "입니다" to be a verb in the same way that we do in English. Instead, it's called a copula and attaches itself onto different words at the end of a sentence, which is why there is no space. Its meaning when translated is still "to be", however.
The tips and notes always refer to the copula as "~이다." I assume that means "~" can stand in for different things in different circumstances, but I have only seen "입니다." Are there other possibilities that mean different things (differing tense, formality, or anything else)?
Why do I need "The". I am not learning English here, "pencil is a thing" should aldo be counted as true. English is not my first language, so why do I be punished for forgetting or neglecting "the", even though I got the translation right? (My mothertonguedoes not have articles)
I don't think I've ever seen space between the noun and the verb. It's only written as one word "물건입니다".
This website lists how to space words, it says do not insert space before verb 이다 : http://www.sayjack.com/blog/2010/06/04/spacing-in-written-korean/