What does this mean (question in the title). I need this to work out a question
A constant is a fixed number. Like 2, or -56, or $\displaystyle \pi$. In this case, the expression $\displaystyle y=kx^2$ where $\displaystyle k$ is constant, it is asking you to consider only one value for $\displaystyle k$ for all values of $\displaystyle x$.