Hi! What is the difference between a T-shirt and an undershirt? I’ve seen white T-shirts (that don’t come in a bag) that look good quality, but some come in white or in some other plain color. Does a T-shirt have to have a print or a logo, or can it be plain and still be considered a T-shirt? I like wearing T-shirts, but I don’t want to end up in “underwear;” that’s what undershirts are. Thank You!