Cold storage refers to storing cryptocurrency on a place where the private key cannot be accessed via the internet. This can be done on a hardware wallet, paper wallet or software wallet in an offline environment.
Bitcoin is a digital or virtual cryptocurrency created in 2009 that uses peer-to-peer technology to facilitate instant payments.
An altcoin is any cryptocurrency or token created after the Bitcoin was developed.
With digital currency, there is a risk that the holder could make a copy of the digital token and send it to a merchant or another party while retaining the original.
Bounties are simple tasks of jobs by the team behind a coin. These can be as simple as joining a Telegram channel or by (re)tweeting. It could also be a bit more difficult like a translation job for example. The participants receive rewards in the form of coins in exchange for completing these bounties.
A block explorer is an online service to track blockchain transactions. It usually is a website where you can see all the new blocks that are being created. You can also search for transactions and wallet addresses. The best-known block explorers are blockchain.info for Bitcoin and etherscan.io for Ethereum.