As it’s entirely dependent on the user agent (ie the browser being used), you are completely at the mercy of how a particular vendor decided to implement it, which means generally you need a pointing device (a mouse) to use it as a tooltip. It isn’t, as far as I know, exposed for keyboard or touch on any browser. From the W3C recommendations:
Warning! Relying on the title attribute is currently discouraged as many user agents do not expose the attribute in an accessible manner as required by this specification (e.g. requiring a pointing device such as a mouse to cause a tooltip to appear, which excludes keyboard-only users and touch-only users, such as anyone with a modern phone or tablet).
You would normally use JS if you want a tooltip, though there are fairly good HTML/CSS-only solutions of you Google around.
To hide it is very simple: just don’t use