What is the difference between "brake lever," shifter," and "gears" when it comes to a racing bike?

Thank you.


A "brake lever" is a lever on the handlebars that you squeeze to operate the corresponding brake.

"shifter" would normally be understood to mean "gear shifter": a lever or other device, usually on the handlebars, that operates the gears.

"gears" generally refers to the overall mechanism involved in changing the drive ratio, including the sprockets and derailleur(s).