What does Arrow in math mean?

Answer 1

A right pointing arrow with two shafts means that if the preceding statement is true then the statement which follows must be true. If it points both ways the two statements mutually imply one another. For example:"all angles of a triangle are equal <=> all sides of a triangle are equal"

An arrow with a single shaft means approaches but never actually reaches the value. This is used to describe limiting value, for example, in calculus.

An upward pointing arrow can be used to indicate a variable or expression increases without limit, whereas a downward pointing one is for positive ones that decrease towards zero.

There are also Knuth's upward arrows, which are used to write Graham's number.