What the mean of this signin mysql <>

Answer 1

"not equal to". It's the same as other languages "!=".

Answer 2

<> is the same with != ( not equal). As a example:

select name from table
where name <> 'Vishal'

This will return all the names tha are not 'Vishal'

Answer 3

This symbol(<>) is used in numbers

Answer 4

Same ideea :)

select students from table
where age <> 18

It selects all students with the age NOT EQUAL TO 18

Answer 5

these are relational operators ... > greater than and < smaller than....
for ex:
select * from employee where salary > 10,000;