Why public key has two parts in my secure messaging client similar to signal
The answer to this question is simple. In simple words, in elliptic curve cryptography, the public key is calculated by multiplying the private key value $s$ with the base point $G$, which results a point on the elliptic curve point: $W = s \cdot G$. This point consists of has two values on the x-axis and one on y-axis if the curve is considered to be within a 2D coordinate system.

Here is a link which gives a good idea of it: ECC with Diffie-Hellman.