Forces: co-planer,con-current and parallel

Forces acting on the same flat surface are co-planar forces. When these forces meet at one point, they're concurrent. Think of three ropes pulling a car from different directions at the same spot – that's concurrent forces.

Bow's notation is a method where you label forces using letters. When drawing a polygon of forces, you arrange them head-to-tail, and the closing line gives your resultant – the single force that replaces all of them. For parallel forces like multiple people pushing a heavy table in the same direction, the resultant is simply their sum.

The equilibrant is the force needed to balance a system completely – it's equal to the resultant but opposite in direction. Reaction forces are what surfaces push back with when you push on them, like the ground pushing up when you stand.