Before I answer your questions, allow me to correct the two sentences. Both of them have grammatical and punctuation errors. 1.) I got some news that makes me a little nervous. We never, ever say "a news," because "news" is one of those nouns that always remains plural no matter what and "a" does not fit with "news" so in this context you should say "some news." "that" in this sentence is used as a "relative pronoun." It functions to refer back to the object in the beginning of the sentence (some news). 2.) I have one goal; that is to go to Tibet before I'm 30 years old. You have two parts of a sentence that are related. They are each separate clauses (each having a subject, verb and object) and therefore must be separated with a semicolon (;). You must use a semicolon, because the second clause offers more information about what the "goal" is. When expressing age, you can either say the number of your age (I'm 30) or the number plus "years old" (I'm 30 years old) "that" in this sentence is very similar to number 1. "that" refers to "goal" in the former sentence. You asked why "1" has just "that" and why "2" has "that is." This is because of the contexts of each sentence is completely different. In 1, that shows how the "news" affects the speaker, thus they say use the verb "makes" instead of is. You would never say "that is me a little nervous" as that would be an incorrect way of expressing it. When we talk about something affecting our feelings or emotions, we often say "x makes me y." For example; "you make me angry!" In 2, "goal" is being defined in the second clause, thus they say "that is." "is" is a form of the verb "to be" which is used to define or give the identity of someone or something. My explanation is quite long, but I hope it is clearer to you. Let me know if you need more examples or explanation. *edit: In 2, a comma might be fine instead of a semicolon, but it feels better with a semicolon to me. Even I could be wrong though. :P

That has many uses in English. 1) In the first sentence, it's cause-and-effect. The cause is "I got news." "That" then carries into the effect, "makes me a little nervous," and signifies it was the news that made the speaker nervous. Another example: "It was the ringing phone that woke me up." The ringing phone was what woke me up. 2) In the second sentence, it's clarification. "I have one goal" is vague. What is your one goal? "To go to Tibet." Saying "that is" means the speaker is aware of their earlier ambiguity and is about to clear up any questions. Another example: "I'm learning a new language, that is, Japanese."