Although 4/4 is by far the most common time signature, another popular choice for music through the ages and including the modern day is 6/8. There are two ways to count a bar in 6/8 time. This can seem unnecessarily confusing when you first encounter 6/8, but as we’ll see the difference is not as big as it first appears.
You can either count it as:
6 eighth-note beats: 1,2,3,4,5,6
2 dotted-quarter-note beats: 1… 2…
The challenging part of 6/8 time is learning to recognize it by ear, or learning to express it yourself when reading from sheet music. That requires the basic theory understanding covered above, but it mostly comes from getting very familiar with the flowing feel of 6/8.