What is the difference between boundary conditions and initial conditions?
I have two condition. The first is a boundary condition
\begin{equation} \theta (\mathbf{x},t)=k(\mathbf{x},t),\hspace{0.2cm}\mathbf{x} \in A, t>0 \end{equation}
And the second is the initial condition \begin{equation} \theta (\mathbf{x},0)=h(\mathbf{x}),\hspace{0.2cm}\mathbf{x} \in B, t=0 \end{equation}.
Why $t=0$ is not taken in boundary condition and in initial condition why not $t>0$?