A block resting on a ramp is pulled down by gravity, yet it only slides along the slope. This diagram explains why: the weight is split into one part that runs down the ramp and one that presses into it, so you can see exactly which force does what.
Weight is a single force that always points straight down. On a ramp, though, the block does not slide straight down — it moves along the slope, while also pressing into it. Because those two directions are what actually matter, engineers rotate their point of view so one axis lies along the ramp and the other is perpendicular to it.
In that tilted frame, the single weight becomes a rectangle's diagonal, and its two sides are the useful components: W sin θ running downhill and W cos θ pressing into the surface.
The red arrow is the weight, drawn straight down from the block. The dashed blue arrows are its two components, and the dashed guides show that the weight really is their diagonal. The green arrow is the ramp's normal force pushing back out of the surface.
Gravity pulls the block vertically downward with a force equal to its mass times g. That single downward force is the starting point for everything that follows.
Instead of horizontal and vertical, we use two directions: one along the ramp and one at right angles to it. The weight is then split into a rectangle whose diagonal is W.
The component running along the slope is W sin θ. It is this part — not the full weight — that actually tries to slide the block down the ramp.
The other component, W cos θ, points straight into the surface. It does not pull the block anywhere; it only squeezes it against the ramp.
The ramp pushes out with a normal force N. With no friction, N exactly balances W cos θ — and the steeper the slope, the smaller W cos θ becomes.
Weight always points straight down, but a block on a ramp moves along the slope, not straight down. Rotating our view so one axis lies along the surface lets us compare forces that actually push the block downhill with the force pressing it into the ramp.
It is the part of the weight that runs parallel to the slope. It grows as the angle θ gets steeper, reaching the full weight only when the slope becomes vertical, and it is the force that tries to slide the block downhill.
It is the part of the weight pressing straight into the slope. It is largest on flat ground and shrinks as the slope steepens, and it sets how hard the block is pressed onto the surface.
The normal force N is the ramp pushing back out of the surface. On a frictionless slope it exactly balances the perpendicular part of the weight, so N equals W cos θ.
Friction acts along the slope, opposing motion, and its size depends on how hard the surfaces are pressed together — that is W cos θ. So a steeper slope both raises the downhill pull and lowers the friction trying to hold it back.