Here's something you should know if you are going to write about fashion (like moi).
A T-shirt is a shirt that is shaped like a "T." It has short sleeves and no collar.
A t-shirt is a shirt shaped like a "t." It has short sleeves and a turtle neck.
A tee-shirt can also be referred to as a golf shirt.
A tea-shirt is a brown, green, black or red shirt, depending on the variety.