why is start and end important regex code example

Example: regex start line

// Match from the start of the line
^
//example:
let str = "HELLO hello world"
let reg = /hello/g //g option: doesn't stop at first match
str.match(reg) // Array(2)["HELLO", "hello"]
reg = /^hello/g //match hello at the start of the string
str.match(reg) // Array(1)["HELLO"]