In western music theory, there are 12 distinct notes. We use the first 7 letters of the alphabet to refer to them. To get from 7 to 12 we additionally use two modifiers that you append to the letter: $\flat$ ('flat') and and $\sharp$ ('sharp'). So, $b\flat$ is pronounced 'b flat' and means 'the note directly below b'. $b\sharp$ is pronounced 'b sharp' and means 'the note directly above b'.

We draw these notes as dots on a staff which consists of 5 straight horizontal lines. This is just so we don't have to carry around a ruler to see how high up notes are on the page relative to the other notes. Here are the 12 notes on a staff:

X:1 L:1/4 K:C A, ^A, B, C ^C D ^D E F ^F G ^G w: a a♯ b c c♯ d d♯ e f f♯ g g♯

Notice there is no note between $b$ and $c$. The same goes for $e$ and $f$. I don't know why this should be the case specifically for these notes.

After the $g\sharp$ on the top, the cycle just repeats itself. If we start on $c$, the sequence of 12 notes looks like this:

X:2 L:1/4 K:C C ^C D ^D E F ^F G ^G A ^A B w: c c♯ d d♯ e f f♯ g g♯ a a♯ b

Or if we start on $g$:

X:3 L:1/4 K:C G ^G A ^A B c ^c d ^d e f ^f w: g g♯ a a♯ b c c♯ d d♯ e f f♯

This is all we need for now.