Ear infections are a common complaint many children experience, especially between the ages of 6-36 months. Some children will grow out of frequent infections as they develop and their ear anatomy changes. What I mean by this is the canal that connects the throat to the inside of the ear, referred to as the Eustachian tube, in an infant is in a horizontal plane compared to an adult. This makes it more challenging for fluids to drain from the ear and easier for viruses or bacteria to stick around. An ear infection most commonly occurs after or during a cold or other respiratory infection.
For more about ear infections, check out this post and other responses to the question: I hate seeing my little girl in such discomfort when she has an ear infection, is there anything I can do at home to help her out?