Alphard is Alpha Hydrae, an orange giant of spectral type K3 at about 177 light years, a cool, swollen, evolved star noticeably reddish to the eye. Its name captures its most striking feature: al-fard, the solitary one, for it shines alone in a wide, dim region of sky with no bright star near it, the single conspicuous light marking the heart of Hydra, the great water-snake that is the largest of all the constellations. That isolation made it an easy star to identify and a natural one to name, a lone beacon in an empty quarter of the heavens.
Hydra's sheer size, the largest of the eighty-eight modern constellations by area, means Alphard's isolation is partly an artefact of how the boundaries were eventually drawn: the snake winds across a full quarter of the sky with very few bright stars along most of its length, so almost any moderately bright star within the modern Hydra boundary would appear similarly solitary. Alphard's evolutionary stage, a swollen orange giant well advanced beyond the main sequence, means it has already exhausted the hydrogen at its core and is fusing helium there instead, a late and comparatively short-lived phase of stellar life. Its wide, dim surroundings have made Alphard a reliable navigational marker for locating the otherwise sprawling and hard-to-trace outline of Hydra as a whole.
Sources AstronomyAndrew Fraknoi, David Morrison, and Sidney C. Wolff (OpenStax) with Almagest (Mathematike Syntaxis)Claudius Ptolemy