Music notation, is the written form of music, and is used for communicating musical ideas. 'Modern staff notation' is probably the most widely used method.
A step-by-step explanation of the modern staff.
The staff (aka 'stave') is the framework for written sheet-music. It is a set of five horizontal lines and four spaces between them that each represent a different musical pitch.
A clef is a symbol placed at the beginning of the staff. It assigns a pitch to one of the lines. There are a few clefs, each of which serve a different set of instruments, based on their register.
The Bass Clef
Also known as the F-clef, it defines the second top line as 'F3' pitch. It is used for instruments with a low register like the Tuba or Double Bass.
The Alto Clef
Also known as the C-clef, it defines the middle line as 'C4' pitch. It is used for instruments with a mid register like the Viola or Trombone.
The Treble Clef
Also known as the G-clef, it defines the 4th top line as 'G4' pitch. It is mainly used for instruments with a high register like the Violin or Clarinet.
Key signatures are how we define scales in sheet music. Each key signature is a different set of sharp (♯) or flat (♭) symbols placed at the beginning of the staff, right after the clef.
Each sharp or flat signs within the key signature, means that all the following notes on that particular line or space are to be played a semitone higher (♯) or lower (♭) than they would otherwise be.
The time signature, which defines the beat count and beat value, will appear right after the key signature.
Bar lines are vertical lines intended to separate between bars.
Notes are placed over the staff according to their pitch height, note length, and position in the piece.
Each note has multiple pre-defined placements on the staff according to each clef. The note 'C' for instance, appears 3 times on a Treble clef. Whenever a note appears above or below the staff lines, a ledger line is added.
Notes have different shapes according to their lengths.
A whole note, that sustain over the period of an entire bar, will look like a hollow oval.
A half note, will sustain half the duration of a whole bar.
A quarter note, will sustain over a quarter period of an entire bar.
A dotted note, will increase the duration of a given note length by a half of itself. A dotted half-note for instance, which normally sustain over a 1/2 bar, will be extended by another 1/4, and as a result, will sustain over 3/4 of a bar.
Notes can be divided into smaller divisions like eighths, sixteenths, or even smaller units like 1/32 or 1/64.
Rests are the silence in music. Similarly to notes, rests have different shapes according to their lengths.
A whole rest, indicate that the whole bar should be silenced.
A half rest, is a silence which will last for half a bar.
A quarter rest, is a silence which will last for a quarter of a bar.
Rests can be divided into smaller divisions like eighths, sixteenths, or even smaller units.
Accidental signs can be added to the left of a certain note. When added, these signs indicate a certain shift in pitch from the note's default pitch and stay relevant till the end of the bar.
Raise the pitch by a semitone. For instance, if a sharp sign is added next to an 'F' note, it will become 'F Sharp', or F♯.
Lower the pitch by a semitone. For instance, an 'F' note with flat sign will become 'F Flat', or F♭.
Reset back to the note's default pitch. Used only after a sharp or flat has been used prior in the same bar.
Whenever multiple notes are aligned vertically, it means that they should be played together. A 'C Minor' chord for instance, is made of 3 notes: 'C', 'E♭' and 'G'.
By now you should be familiar with the basic components of staff notation.