Since it incorporates meter and time, "rhythm" is a crucial part of how the music feels. However, whereas meter simply tells you how many beats, rhythm is how those beats are used.  Try this: tap your finger on your desk, and count 1-2-3-4 1-2-3-4, steadily. Not very interesting, is it? Now try this: on beats 1 and 3, tap louder, and on beats 2 and 4, tap softer. That's got a different feel to it! Now try the reverse: tapping loud on 2 and 4, and soft on beats 1 and 3. Check out Regina Spektor's Don't Leave Me. You can clearly hear the rhythm: the quieter bass note happens on beat 1 and beat 3, and a loud clap and snare drum happens on beats 2 and 4. You'll start to get a sense of how music is organized. That's what we call rhythm! Each footstep will equal one beat. Those are represented musically by quarter notes, because in much of Western music (meaning music of the western world, not just the music of Hank Williams!), there are four of these beats for every measure. Musically, the rhythm of your walking will look like this:  Each step is one quarter note. On a sheet of music, quarter notes are the solid black dots attached to stems without any flags. You can count that off as you walk: "1, 2, 3, 4-1, 2, 3, tw Quarter notes are referred to as "crotchets" in some places, such as the UK.  If you were to slow your pace down to half that speed, so that you only took a step every two beats on the 1 and on the 3, that would be notated with half notes (for half a measure). On a sheet of music, half notes look like quarter notes, only they aren't solid black; they are outlined in black with white centers. In some places, half notes are called "minums". If you slowed your pace down even further, so that you only took a step every four beats, on the one, you would write that as a whole note—or one note per measure. On a sheet of music, whole notes look like "O"s or donuts; similar to half notes without stems. Enough of this slowing down. As you noticed, as we slowed the notes down, we started taking away bits of the...

TL;DR in Vietnamese:
Hãy cảm nhận nhịp điệu. Hãy tưởng tượng mình đang đi bộ. Hãy tăng tốc độ lên! Chùm các nốt. Tìm hiểu giá trị của dấu nối và dấu chấm dôi. Dấu lặng.