Definite Integral: The definite integral of a function over an interval $[a, b]$ gives the net area under the curve from $a$ to $b$.
Riemann Sum: A method for approximating the total area under a curve by dividing it into smaller subintervals and summing up areas of rectangles formed within these subintervals.
Fundamental Theorem of Calculus:$\text{Part I}$: It states that if $f$ is continuous on $[a, b]$, then its indefinite integral is differentiable and its derivative is $f$. \n$\text{Part II}$: It states that if $F$ is an antiderivative of $f$ on $[a, b]$, then \(\int_{a}^{b} f(x) \, dx = F(b) - F(a)\).