1. Describe the concept of public and private key with your own words.
A public key is required by the public to send encrypted data to the private key owner, then the owner decrypts the data using his private key.
2. What 2 use-cases can public key cryptography be used for?
You/your computer generates a private key, that you use yourself and that you should NOT share with others. From this private key, you can create a public key. The public key can be posted online or send to others. Others can use this key to send you encrypted messages, which only your private key can decrypt into the original message. With this it allows for enclosed communication on an open network.
Encryption and Digital signature.
Private keys are random numbers generated by one’s computer (they are to be kept safe).
Public keys are derived from private keys and known from the public.
You can only go from a private key to a public key and not the other way around.
Encryption and digital signature,
A private key can generate a public key which can receive encrypted messages that only the private key can decipher. It is impossible to figure out the private key from the public key.
A private key is an extremely large and highly random number. A public key can be derived using a one-way function from the private key. The public can be shared with other people while the private key is know only to the owner.
Two use-cases of public key cryptography are: encryption and digital signatures. Encryption allows someone to encrypt a message using the receiver’s public key, but the encrypted message can only be decrypted using the receiver’s private key. This means the message can be kept secure over an open and unsecured communication channel. Public key cryptography also allows robust authentication to verify the integrity of a message/transaction by means of verifying the sender via a digital signature. A sender can combine a message with a private key to create a digital signature on the message. The recipient can compare the digital signature with the sender’s public key and can mathematically verify if the signature corresponds with the public key and is therefore valid. Bitcoin uses public key cryptography to send and verify transactions. Any legitimate private and public key pair is automatically a legitimate bitcoin address.
1.Describe the concept of public and private key with your own words.
The public key is the key anyone can access, the private key is your own key. If you want to send a message or proceed to a transactions with someone else you will need both. The public key will be opened to anyone but your private key will be encrypted if you want to send it to someone the mathematics will convert it so it is only readeable by the one you’ve send it to.
A private key is a large random number that is kept secret by its owner, while the public key is shared with the world. Using a one-way function the public key is derived from the private key.
Encryption: The private key is used to decrypt a message that was encrypted with the public key.
Digital signatures: The private key is used to generate a signature for a message (usual applying the private key to a hash of the message). Then, the public key allows to verify that this signature was created by the owner of the private key.
(Example procedure: Encrypt hash with private key to get a signature. Decrypt signature with public key and compare with hash of the received message.)
The private key is kept private and is used to decrypt the data.
A private key is a randomly generated number containing a significant number of digits in ASCII form. A public key is a shorter but still long string of numbers generated from the private key using a specific mathematical function. The public key is used as a identifier that can be used ‘publicly’ on the internet to transact with other entities. The public key is visible to others. A private key is known only to the owner. A private key cannot be derived from the information in the public key.
Here encryption is only for yourself without sharing over a network. If you want to share a message /payment to another users public key, you alway need a digital signature
Elections would probably utilize digital signatures same as cryptocurrencies. Public key cryptography can also be used for encryption. 
Thanks Fabrice! Makes sense - changed my notes accordingly. Cheers 
Describe the concept of public and private key with your own words.
The combination is used to encrypt and decrypt data so you can securely send it over the network.
What 2 use-cases can public key cryptography be used for?
Encryption, decryption(digital signature).