Let $M$ be an $n$-dimensional $C^{\infty}$ manifold. Two vector fields $X$ and $Y$ on $M$ that never vanish is said to have the same direction if their tangent vectors $X_p$ and $Y_p$ have the same direction for each $p\in M$. Can anyone kindly clarify what is meant by the statement "their tangent vectors have the same direction" ?.
Thanks in advance.