At and In,

"At" and "In" are prepositions used in English language to indicate location or state. "At" is used to point out specific locations or points in time. For example, "I will meet you at the park," or "She arrived at 5pm." "In" is used to describe a location within a larger area, it can also denote a state or condition, or the form or shape of something. For example, "She is in the library," "He is in trouble," or "They came in pairs." It can also be used to indicate a period of time, like "in the morning" or "in 2020."