Indefinite Integral: This is the antiderivative, or reverse process, of differentiation. It's called 'indefinite' because it includes a constant term whose value isn't specified.
Definite Integral: This is an integral with specific start and end points. Unlike an indefinite integral, it doesn't include a constant of integration because its value depends only on these two points.
Initial Condition: In calculus, this refers to the known value of a function at a specific point in time or space. It's used along with differential equations to find particular solutions.