As the question has been accurately answered it's time for a story from my youth where the term was used inaccurately.
Growing up in New Jersey, my mom was frugal and stretched the budget with powdered milk. Us kids were rather disappointed in powdered milk of the day and didn't drink it. Her solution was to mix whole milk and powdered milk half-and-half. And so it was called. And we still didn't like it but it was tolerable.
The first time I ran into the term half-and-half in a cooking context I wondered why anyone would willingly use the
The modern powdered milk is much better than the late 60s version was and I do occasionally have a cooking use for it, usually backpacking or other limited access outdoor cooking.
Half-and-half has 11.5% butterfat, as opposed to light cream (aka coffee cream) which has between 18 and 30% and whole milk which has 3.25%. So if you mix 1/2 light cream and 1/2 whole milk, you'll be pretty close. If you use heavy cream, the outcome will be richer (and probably tastier ) -- but whether or not it's better depends on the recipe.