They were used extensively, it is more common nowadays to use reinforced concrete or composite sleepers.
To reduce the pressure exerted by train
Wooden sticks (thick) and iron.
I believe the rails were wooden.
When sleepers are placed below the rails, the area of cross-section is increased. We know pressure= Force/Area. When the trains run on the rails, the pressure is small because of large area of cross-section of the sleeper. Hence, ground will not yield under the weight of the train.
To keep the rails at a certain spacing, and to spread the weight of the train over a wider area.
In 1550, engineers in Germany developed an early ancestor to railroads. They made wooden rails that allowed wooden horse-drawn wagons easier movement over muddy dirt roads. The Coalbrookdale Company improved the concept by adding plates of cast iron to wooden rails. In 1789, William Jessop, and English civil engineer, revealed the first use of edged metal rails to be used with flanged wheels. Many historians credit the Surrey Iron Railway in south London as the world's first public railway (even though the carts still were pulled by horses).
This is difficult to answer because depending upon the area and the railway, and era, the answer is different. The early railroads used wooden rails with steel straps on top, which was followed by iron rails. Initially, these were built on stone "sleepers", but later were built on wooden sleepers or ties. In the Southern US, many railroads were built on "stilts", essentially bridges because of the wetlands/swamps they travelled through.
Skateboarding rails are used for tricks on the skateboard. The rider can jump up on the rails and slide or "ride" the rail and jump off at the end. These rails are included in most skate parks or skate circuit design.
The width apart of rail tracks are set to the gauge of the trains and carriages that are allowed to run on those tracks. They are kept in position by wooden sleepers, though concrete sleepers are often used nowadays.
A cot top changer is a flat surface that sits on top of a baby's crib walls, so that a baby can be changed on that surface. They are often wooden, and have small rails on the sides.
A golden spike was a railroad spike used in celebrating the wedding of the rails.
The railroad spike used in celebrating the wedding of the rails was the golden spike.