A cubic C x1 y1 x2 y2 x y leaves toward control point 1 and arrives at x y from control point 2; S x2 y2 x y mirrors the previous control point so a chain has no kinks. The quadratic Q x1 y1 x y has one control point, and T x y mirrors it. The arc A rx ry rotation large-arc sweep x y names an end point and radii, and two flags pick one of four arcs: large-arc 1 goes the long way round, sweep 1 goes clockwise.
<svg width="630" height="130" fill="none" stroke-width="3">
<path d="M10 110 C 40 10, 150 10, 180 110" stroke="#1f5f8b"/>
<path d="M10 110 L40 10 M150 10 L180 110" stroke="#90a4ae" stroke-dasharray="4 3"/>
<circle cx="40" cy="10" r="4" fill="#90a4ae"/><circle cx="150" cy="10" r="4" fill="#90a4ae"/>
<path d="M210 65 Q 245 5, 280 65 T 350 65 T 420 65" stroke="#e09a10"/>
<g transform="translate(520 65)">
<path d="M-30 0 A 35 35 0 0 0 30 0" stroke="#3f7d3a"/> <!-- small, ccw -->
<path d="M-30 0 A 35 35 0 0 1 30 0" stroke="#b5452f"/> <!-- small, cw -->
<path d="M-30 0 A 35 35 0 1 0 30 0" stroke="#5b3f99" stroke-dasharray="6 4"/>
<path d="M-30 0 A 35 35 0 1 1 30 0" stroke="#2a9d8f" stroke-dasharray="6 4"/>
</g>
</svg>
Between the same two points you get the short green and red arcs and the long dashed ones. A too-small radius is scaled up until the arc fits.