The latest two posts have been about two elliptic curves used in cryptography. Elliptic curves have an addition law, which can be bootstrapped into multiplication. This multiplication can be done efficiently, but it cannot be undone efficiently. This is analogous to RSA encryption, which depends on the fact that large primes can be multiplied efficiently but cannot be factored efficiently.
The first, Monero’s elliptic curve, is about Ed25519, the curve Monero uses in digital signatures. The reason for the curves name is explained in the post. The post fills in some details that are often left out of the description of the curve and its use.
The second post explains an equivalence between Ed25519 and Curve25519. You may be using Curve25519 as you read this since it is commonly used in secure web pages (TLS).
The two elliptic curves, Ed25519 and Curve255219, have properties in common, as their names suggest. The curves are not isomorphic as elliptic curves, but their group structures are isomorphic, which is all that cryptographers care about.
Enjoy!