Here we must assume that f(t) is such that the integral exists (that is, has some finite value). This assumption is usually satisfied in applications—we shall discuss this near the end of the section.
Not only is the result F(s) called the Laplace transform, but the operation just described, which yields F(s) from a given f (t), is also called the Laplace transform. It is an “integral transform”
with “kernel” k(s, t) e st.
Note that the Laplace transform is called an integral transform because it transforms
(changes) a function in one space to a function in another space by a process of integration that involves a kernel. The kernel or kernel function is a function of the variables in the two spaces and defines the integral transform.
Furthermore, the given function f(t) in (1) is called the inverse transform of F(s) and is denoted by l 1(F ̨ ); that is, we shall write