Linear kinematics is not necessarily the easiest but it's usually the first division of a student's study of physics in high school. It's name tells nearly all one needs to know -- motion (kinematics) in a straight line (linear). In middle school we learn the simplest case, that where acceleration is 0. There, in pre-algebra, we learn that distance = rate x time. This will be the first equation we examine in physics, although we will change it a bit. First, physics has a bunch of "rates", so instead of "r" we'll use "v" for velocity. Velocity describes the "rate of change of position (over time)". Depending upon what class you take we'll use "d" for distance or "s" for distance. Everyone uses "t" (lower case) for time. We'll also rearrange and express the equation as v = Δd/t in this manner defining velocity as the rate of change of position.
Linear motion may be uniformly accelerated. Acceleration is the rate of change of velocity (again over time). If the acceleration is uniform for a length of time it is given by: a = Δv/t. If acceleration is 0 or otherwise uniform, the average velocity is simply the arithmetic mean of the initial and final velocities (v(avg) = (v1 +v2)/2). The equations below can be derived from the three relations already mentioned.
In this set of equations x is used for position, "0" to indicate an initial condition.