I hear this certain term in Monero sometimes but what does it mean? Is it related to mining maybe?
In a cryptocurrency network (like Monero and Bitcoin), miners are finding solutions to blocks. When a solution is found, the miner has created a block and this new block can now become the tip of the blockchain (the newest block).
In order for this block to become the tip of the blockchain, the block has to get to every node in the network - the block has to propagate. This occurs through the peer to peer network. The miner creates the block, and sends it to the peers it is connected to. These peers validate the block, and then relay it to their peers.
This is block propagation.