Cairo is a programming language for writing provable programs, where one party can prove to another that a certain computation was executed correctly. Cairo and similar proof systems can be used to provide scalability to blockchains.
StarkNet uses the Cairo programming language both for its infrastructure and for writing StarkNet contracts.
python3.9 -m venv ~/cairo_venv
source ~/cairo_venv/bin/activate
pip3 install ecdsa fastecdsa sympy
pip3 install cairo-lang