An eighth note, also called a quaver is a note played for one eighth the duration of a whole note (semibreve). It lasts a quarter of the duration of a half note (minim) and half of the duration of a quarter note (crotchet). In 4/4 time a whole note lasts for four beats. An 8th note lasts for half a beat. Two of these notes make up a quarter note.
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How do you draw an 8th note? It is notated with an oval, filled-in note head and a straight note stem with one flag. (16th notes have two flags. Quarter and half notes have no flag.) Generally, (like all notes with stems) when quavers are below the middle line of the staff, they are drawn with stems to the right of the notehead, facing up. When they are on or above the middle line, the notes are drawn with stems on the left of the note head, facing down. 
Stems can be used to indicate voicings or parts. Stems for the upper voice’s notes are drawn facing up while stems for the next lower part’s notes are drawn facing down, no matter what position they are on the staff. That way voices/parts are clear to the player and singer.
As for the flags, they are drawn on the right side of the stem and curve to the right. For stems facing up, the flags starts at the top and curves down. For stems facing down, the flags start at the bottom of the stem and curve up. When there are multiple notes, instead of flags, the notes are beamed together, as shown in the diagram with notes beamed together below (left).
To count eighth notes, set your metronome to let’s say, 60 beats. (If you don’t have one, you can search for ‘metronome’ in the search engines and get a free online metronome.) Count “one and two and three and four and, one and two and three and four and” and so on. “One, two, three and four” falls directly on the beat (click) while the “ands” lie between the beat.
The following video shows you how to count eight notes, quarter rests, and there are a few half rests in there as well.
An eighth note has the same duration as an eighth rest (quaver rest). When you see an eighth rest you are not to play anything for the duration of that rest – half a beat. An eighth rest has 1/8 the duration of a whole rest. It resembles the number, 7.
Go here for a large, printable eighth note.
Go here for two large beamed ones.
Piano notes and keys – Learn the notes which correspond to the keys on the piano.
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