t</em>&rdquo; means <em>getting out of the keyframe</em>, <em>after</em> it. That&rsquo;s what&rsquo;s called the <em>keyframe ease</em>.<br />
In other animation software, the interpolation is defined between two keyframes (which is more logical and makes more sense mathematically speaking: there can&rsquo;t be any interpolation for a single keyframe, one always needs <em>at least two</em> keyframes to interpolate).<br />
In this latter case, &ldquo;<em>in</em>&rdquo; means <em>getting in the interpolation