When a note is sharpened it is raised. When a note is flattened it is lowered. The keyboard in the video shows some sharps # and flats ♭.
A semitone is one step on the keyboard, or the distance between two notes. A tone is two steps on the keyboard or two semitones put together.
Enharmonic notes
An F# is the same as a G♭. A B♭ is the same as an A#. These are enharmonicNotes which have different names but are the same pitch. notes - they are described differently but have the same pitch.
