Step 1: Recall the relation between acceleration, velocity, and displacement.
\[
a = v\frac{dv}{ds}
\]
Step 2: Rearrange the equation.
\[
a\,ds = v\,dv
\]
Step 3: Integrate both sides.
\[
\int a\,ds = \int v\,dv
\]
\[
\text{Area under } a\text{–}s \text{ curve} = \frac{v^2}{2}
\]
Step 4: Interpret the result.
\[
\frac{v^2}{2} = \text{kinetic energy per unit mass}
\]
Hence, the area gives the change in kinetic energy per unit mass.
Final Answer:
\[
\boxed{\text{Change in kinetic energy per unit mass}}
\]