Our Time Signature for this page is 4/4 which means that there are four quarter beats in a measure. Here is an empty staff with one measure:
What can we fill it with?
A whole note takes up four beats, or the entire measure. It has a hollow note head, and does not have a stem or any flags.
A nalf note takes up two beats, or half the measure. Because it takes two beats, we can put two in this measure. A half note has a hollow note head and a stem but no flags.
A quarter note takes up one beat, or a quarter of the measure. Because it takes one beat, we can put four of them into this measure. A half note has a solid note head and a stem, but no flags.
The eighth note takes up 1/2 of a beat, or an eighth of the measure. We can fit eight of them into this measure. An eighth note contains a solid note head, a steam and one flag. Since their are eight of them in this measure, the eight note gets "Beamed".
Notes that are an eighth note or smaller can have their flags beemed togeather in groups equal to a quarter note. In the Eighth note example above the eighth notes can be beamed in pairs of two:
Some composers will beam four eighth notes togeather, but two is the standard.
Sixteenth notes are half the value of a eighth note and look like eighth notes with an extra flag. They can be beamed in groups of four:
Four of these sets can be inserted into a measure.
Any combination of these notes can be inserted into a measure so long as they add up to four beats: