What is Kinetic and thermodynamic control?

Example 9.18 (Choosing the product)

A reactant gives B over a barrier of $50\,\mathrm{kJ}/\mathrm{mol}$ ($\Delta E = -10\,\mathrm{kJ}/\mathrm{mol}$) and C over a barrier of $70\,\mathrm{kJ}/\mathrm{mol}$ ($\Delta E = -40\,\mathrm{kJ}/\mathrm{mol}$). At $300\,\mathrm{K}$ and short times, with equal pre-exponential factors, B forms $\exp(20000/(8.314 \times 300)) \approx 3000$ times faster than C: kinetic control gives B. At high temperature and long times, B returns over its small reverse barrier, C does not, and the system ends as C: thermodynamic control.