Is $.get of jquery asynchronous?

Yes, $.get is asynchronous. From the documentation:

This is a shorthand Ajax function, which is equivalent to:

$.ajax({
  url: url,
  data: data,
  success: success,
  dataType: dataType
});

...and as that doesn't have the async option, async defaults to true. (Note that async will be going away entirely in a future version of jQuery; it will always be true.)

If $.get is asynchronous then what's the point of $.ajax?

$.ajax gives you control over lot more options. $.get is just a shortcut.

$.get is simply a shorthand for:

$.ajax({
  url: url,
  data: data,
  success: success,
  dataType: dataType
});