What Is the Concept of ‘K’ in the $x Y = K$ Formula, and How Does It Change?

'k' represents the constant product of the reserves ($x$ and $y$) in the pool. It is a mathematical invariant that ensures the pool remains balanced after every trade.

'k' is not a fixed number forever. It increases when new liquidity is added to the pool and decreases when liquidity is removed.

Trades alone do not change 'k'; only changes in total liquidity reserves alter its value.