Quote marker とcan be used to quote someone’s speech :

勅使河原さんは来週来ると言いました = Mr. Teshigawara said that he will come next week.

(てしがわら/勅使河原 = Testhigawara. さん = Mr. は = particle. らいしゅう/来週= next week. くる/来る = to come. と = quote marker. いいました/言いました = said.)

The sentence above is an example of an indirect quote. To quote someone indirectly, use this general formula :

plain form of the verb, adjective or copula + と言う

The sentence above is an example of someone being quoted indirectly, but this next sentence is used when someone is quoting another person by using their exact words :

「早く寝てください。」と勅使河原さんは言いました = Mr. Teshigawara said, “Please sleep early.”

(はやく/早く =  early. ねてください/寝てください = Please sleep.)

If the sentence above was an indirect quote, it would say, “Mr. Teshigawara said to sleep early.” Also, this symbol  「」is equivalent to the quotation mark  “ ” used in English.

Quote marker と can also be used to express thoughts :

その人は犯人だと思った= I thought that person was a criminal

(その = that .  ひと/人 = person. は = particle.  はんにん/犯人 = criminal. だ = past tense affirmative of です. と = quote marker. おもった/思った = thought)

To express that you don’t think something is the case, use ~ないと思います

勅使河原さんは起きないと思います = I don’t think Mr. Teshigawara will wake up (literally : I think Mr. Teshigawara will not wake up)

(てしがわら/勅使河原 = Teshigawara. さん = Mr. は = particle. おきない/起きない = not wake up. と = quote marker. おもいます/思います = think.)

Quote marker とcan be used to explain what you heard :

総理大臣は日本に帰ると聞きました = I heard that the Prime Minister will return to Japan.

(そうりだいじん/総理大臣 = Prime Minister. は = particle.  にほん/日本 = Japan. に = particle.  かえる/帰る = return. と = quote marker.  ききました/聞きました = heard.)