I'm making a sourdough starter and the recipe says to cover. Does thatmean air tight.

Some culture-growing wisdom has it that you are seeking to capture naturally present airborne beasties to get things going in a new starter. I dunno-- I used an organic raisin when I birthed mine many years ago. In any case, an active starter will produce CO2, so keep it loosely covered unless, as already stated, it's being held in the fridge.
Happy sourdough-ing!

I only cover my starter airtight if it's in the fridge.

If your starter is sitting out, you can leave the lid ajar or cover the container with a cheesecloth. That way the yeast in the air can get in your starter!