Mince Pies, like Christmas Puddings, were originally filled with meat, such as lamb, rather than a dried fruit mix as they are today. They were also first made in an oval shape to represent the manger that Jesus slept in as a baby, with the top representing his swaddling clothes.
During the Stuart and Georgian times, in the UK, mince pies were a status symbol at Christmas! Very rich people liked to show off at their Christmas parties by having pies made is different shapes (like stars, crescents, hearts, tears, & flowers); they fancy shaped pies could often fit together a bit like a jigsaw! They also looked like the 'knot gardens' that were popular during those periods. Having pies like this meant you were rich and could afford to employ the best, and most expensive, pastry cooks!
Now they are normally made in a round shape and are eaten hot or cold. I like mine hot with some ice cream!