Abba is a band, they have many songs including dancing queen, and // fernando. abba is actually a swedish band, so if we wanted to find // out howswedish a string is, we could simply find out how many times // the string contains the substring "abba". we want to look for this // substring in a case insensitive manner. so "abba" counts, and so // does "abba". we also want to check for overlapping abba's such as // in the string "abbabba" that contains "abba" twice.