Last updated: June 2024 / 846333 o'block
Sats/satoshi are a subunit (fractions) of bitcoin, same as cents are subunits of dollar or euro.
They are named to honour the creator of Bitcoin, Satoshi Nakamoto.
Sats are the base unit of the blockchain. When specifying an amount of bitcoin, the source code uses satoshi.
100 000 000 sats = 1 bitcoin
There's a handy btc/usd converter on Kraken.
Bitcoin can be divided further into 1/1000 of a satoshi in a lightning payment channel.
More on Bitcoin units: https://en.bitcoin.it/wiki/Units
When people say "stacking sats" they mean accumulating more savings in bitcoin.
I'm unaware of any generally agreed-upon capitalisation convention, but on this site, I'm using 'Bitcoin' - with capital B - when talking about the protocol/network, and 'bitcoin' - with lowercase b - when talking about the unit of account or bitcoin as actual money.