I once read, that one should use optimized/specialized fonts for headings and titles.
This can be a good idea, though you don't have to.
In early days of type, type cutters had to make different cuts of a typeface for different sizes. Because computer fonts didn't exist, they couldn't just rescale at whatever size they wanted to print, they had to have a different cut of the font with the metal pieces at the right size.
So this is where the concept originates. Naturally, type cutters began to make subtle differences in the type designed for each size to account for optical effects. Smallest sizes called for proportionally fatter strokes, a little more loose spacing, and sometimes even a few details simplified, so it could be read easier at that size. But very large type, for "titling", could have lovely ornate thin strokes and tighter spacing. The net effect however was that the ordinary reader probably would not notice the subtle differences, it'd just look nice at large sizes and yet still be highly readable at small sizes.
Check out this image showing how William Caslon had to make lots of different "cuts" of his typeface for different sizes.
Modern font foundries like to sell groups of fonts in "families" now, but usually not for different sizes (since computer fonts are infinitely scalable anyway) but for different weights and styles. Occasionally, however, they'll often throw in a "titling" variant which is subtly different to the "book" variant. Usually this just means it eases off on some of the optimisations made to the book variant in order to make it readable at small sizes. So it may have thinner strokes in some places, and tighter spacing, and include detail that may have been lost had it been included at small sizes. Plus you can usually depend on it having paid a lot of attention to kerning (though from a decent foundry, this should be true of all styles).
As for whether you need this - it's up to you. If a typeface looks as good small as it does big (on your target medium, so if it's printed, previewing it on-screen won't help), then there's nothing stopping you from just using the same thing. But if you have a titling variant and it didn't cost you anything extra, you may as well use it.
For display, like on posters, logos, etc, you'll want to be tightening up the kerning and stuff by hand anyway, usually. But when you want a mechanism to display headings and you want something already pre-kerned nicely for that purpose it can be handy to have a titling font.
It's far more common to use a font with a completely different typeface for body text and titles these days, rather than use the same typeface for both. So a lot of the time this is moot.