Music notation not only shows us the rhythm of the music but also the pitch. Pitch is shown by use of five lines and four spaces which we call a staff.
A clef is added to the staff to locate a particular pitch on the staff. Each line on a staff represents a different pitch and each pitch has a letter name from A to G in the alphabet. The two most common clefs are the treble and bass clefs.
The Treble Clef indicates where 'G' above middle 'C' is located on the staff. It curls around the second line up on the staff - this is where 'G' is located. It was originally a fancy letter 'G' and it can also be called a G Clef.
An Octave is the distance between any note and the next note of the same name either above or below it. The example shows three octaves of the pitch 'C'.
An Octave Sign indicates that you should play the note one octave higher or lower. It can be used to avoid using too many ledger lines.
When placed above the staff it means to play one octave higher. The symbol is 8va or sometimes only 8. It may be followed by a dashed line to indicate how many notes are affected by the symbol.
When placed below the staff it means to play one octave lower. The octave down symbol may look the same as the octave up symbol or it may be 8vb or 8 basso.
When a note with a stem is below the middle line, it should have the stem go up on the right side of the note. When a note is above the middle line, it should have the stem go down on the left side of the note. And when a note is on the middle line, the stem can go whatever direction looks best.
When notes are beamed together, then the stems should go whatever direction fits the majority of the notes.