I dont understand how can velocity be expressed by vectors.

I am a highschool student, and I hardly know about the physics. All i know about vectors is just they are something like arrows and expressed by numerals in symbols like [] this. I dont know well even how vectors can be used in this field. I want to know the relationship between physics and vectors and how vectors are defined in physics. (Im sorry. I am not a native speaker of English. I think there can be weird expressions.)